Talk:Paper - On the relative growth of the component parts and systems of the albino rat (1912)
On The Relative Growth Of The Component Parts (Head, Trunk And Extremities) And Systems (Skin, Skeleton, Musculature And Viscera) Of The Albino Rat
C. M. Jackson And L. G. Lowrey
From the Anatomical Laboratory of the Unirersity of Missouri
Two Figures
To comprehend fully the growth of the body, the following data are reqmred: (1) the growth of the body as a whole; then an analysis to determine (2) the growth of the principal parts; (3) the growth of the various systems; (4) the growth of the individual organs; and finally (5) the growth of the ultimate constituent tissues and cells. Observations upon these various phases of growth in different animals are scattered through the literature, but in no case are they sufficiently complete to afford a comprehensive view of the process of growth in any individual species. In the case of the albino rat, the growth of the body as a whole and of the central nervous system has been carefully studied by. Donaldson and his associates. The present paper will give a partial analysis of the growth process in this animal, including the relative growth from birth to maturity in the various constituent parts and systems of the body. A more extensive study of the growth and variation in the individual viscera will be published soon in a separate paper.
MATERIAL AND METHODS
Ninety-three albino or white rats (Mus norvegicus albinus) were utilized for the present paper. These include 18 newborn (9 males, 9 females) ; 19 at 1 week (8 m., 11 f.) ; 13 at 3 weeks (7 m., 6 f .) ; 14 at 6 weeks (6 m., 8 f .) ; 10 at 10 weeks (5 m., 5 f.) ; 13 at about 5 months (6 m, 7 f .) ;-and 6 at about 1 year (4 m., 2 f .) . They
449
THE ANATOMICAL RECORD, VOL. 6, NO. 12 DECEMBER, 1912
450 C. M. JACKSON AND L. G. LOWREY
were fed daily with wheat bread soaked in whole milk, and a supply of chopped- corn was kept constantly in the cages. In addition, they were fed fresh meat (beef) once a week. They were well cared for in an animal house, and represent well-nourished, healthy animals. In a few of the older animals, the lungs were infected, but none is included in which the infection was apparently sufficient to affect the general nutrition or vigor.
The various litters were kept separate and are indicated in the tables. Wntiile the number of animals is not large (on account of the laborious method of dissection) , it is sufficient to give some idea of the average condition and of the extent of variation. Since the personal equation is likely to enter to a certain extent in the process of separating the muscular and skeletal sj^stems, etc., in dissection, those litters dissected by Lowrey are designated by the prefix A or M with the litter number. Those without prefix (including all the observations given for the head, trunk and extremities) were dissected by Jackson.
The method of dissection was as follows. The animal was taken in the morning before feeding and killed by chloroform. The gross body weight, and the lengths of body and tail were recorded. The head was then removed (just posterior to the foramen magnum and anterior to the larynx) and weighed. In the meantime, the trunk was suspended and the blood (unmeasured) was allowed to escape. Then the viscera were carefully removed and weighed individually (including brain, -spinal cord, e3'eballs, thyroid, thymus, heart, lungs, liver, spleen, stomach and intestines, both with contents and empty, suprarenals, kidneys and gonads. Urine was estimated if present. The extremities were separated at the shoulder and hip joints and weighed. The skin was next removed (including ears, claws and adherent subcutaneous tissue) and weighed. Then the musculature with skeleton was weighed, the few remaining additional structures (genitalia, large vessels, pharynx and oesophagus, larynx and trachea, and masses of fat connected with the musculature) having been carefully removed. Finally the musculature was carefully dissected off and the skeleton, including bones, cartilages and ligaments, was weighed. This weight, subtracted from that
GROWTH OF THE ALBINO RAT 451
of the skoloton and niiisrulatiiro to{i;cthor, gives the weight of the inuscuhituie, inchuliug the teiulous. Evuporatioii was reduced to a luiiiimum by keeping the various structures in a closed moist container, so far as possible. The net body weight, which is the gross body weight minus contents of stomacli, intestines and urinary bladder, was used as the basis in calculating the percentage weights. The percentages are therefore slightly higher than they would be if calculated upon the gross body weight. The ditference is not of material importance in the case of the albino rat. however, as the contents do not average more than 5 per cent of the body at the ages observed (excepting at 6 weeks, where the average was about 8 per cent.
The observations were grouped at seven ages, chosen for the following reasons. At 1 week the weight at birth has about doubled. At 3 weeks, it has about doubled again, and this moreover is the age at which the animal is usually weaned. At 6 weeks, the body weight has again about doubled, and the animal is well established upon its permanent diet. Ten weeks represents the age of puberty, and the body weight of 6 weeks has again about doubled. At 1 year, the bod}' weight has again nearl} doubled, and this represents nearly the adult weight. Five months was arbitrarily selected as the time when the body weight is approximately half w^ay between those of 10 weeks and 1 year. While therefore observations are not available for the various intermediate age periods, these are sufficientlj close together so that no important change in the relative weights of the constituent parts is likely to be overlooked. Moreover, on account of the variations at the different ages in the body weights, these form a fairly continuous series; and the relative weights of the various constituent parts are apparently more closely correlated with the body weight than with the age.
Observations (by Jackson) upon 5 wild gray or brown rats (Mus norvegicus) are also included for comparison, in tables 5 and 6. These rats were captured by traps in barns, and were probably chiefly grain-fed.
For the sake of economy of space, and since the present paper is concerned primarily with the relative weights, the percentage
452 C. M. JACKSON AND L, G. LOWREY
weights only are recorded in the tables. The absolute weight of the' body (net) is given in all cases, however, from which the absolute weight of the individual parts can easily be calculated if desired. Moreover, the original data will be deposited in The Wistar Institute of Anatomy in Philadelphia, where they will be accessible to any who may care to use them.
RELATIVE GROWTH OF THE COMPONENT PARTS
1. Head (tables 1, 2, 5; fig. 1). In the limited series of data given in table 1, it will be noted that, on the average (table 2), the head increases from 21.65 per cent of the body in the newborn to 23.70 per cent at 1 week; decreasing to 20.22 per cent at 3 weeks, 11.80 per cent at 6 weeks, 9.56 per cent at 10 weeks, 9.42 per cent at 5 months, and 9.29 per cent at 1 year. In a much larger series, however, including 20 or more of each sex at each age (observed by Jackson in a study of the growth of organs), the relative weights were found to average somewhat higher, being 23.43 per cent, 25.74 per cent, 24.27 per cent, 15.17 per cent, 11.21 per cent, 10.47 per cent and 10.75 per cent, respectively (data in parentheses in table 2.) This is to be explained partly on account of individual variations in the smaller series, and partly as due to correlation with the body weight, which in all cases averages heavier in the smaller than in the larger series of corresponding age. In constructing the diagram in Fig. 1, the data from the larger series were used.
No difference in the relative weight of the head (aside from that due to different body weight) is evident between the sexes; and the small series of observations on the gray rat (table 5) shows the head to be of approximately the same relative size as in the albino.
Fig. 1 Change in the percentage weight of the component parts of the albino rat. The width in the vertical direction) of each strip is proportional to the percentage weight of the corresponding part. The percentage weight is indicated for every part at each of the ages. Up to the age of 10 weeks (that is, in the ruled portion of the figure), the horizontal distance is drawn to scale, proportional to the age. Beyond 10 weeks, the horizontal distance is not in proportion to the age.
GROWTH OF THE ALBINO RAT
453
454
C. M. JACKSON AND L. G. LOWREY
50b 50b 50b
TABLE 1 Albino rat— Percentage iveight of the head, trunk and extremities Newborn
LITTER NUMBER
SEX
NET BODY WEIGHT
HEAD
UPPER EXTREMITY
LOWER EXTREMITY
TRUNK
47
m.
grams
5.88
per cent
22.60
per cent
7.27
per cent
9.70
per cent
60.43
47
m.
5.96
22.40
7.57
8.49
61.54
47
m.
6.25
21.12
8.45
8.00
62.43
62
f.
4.27
21.08
7.07
9.62
62.23
58
f.
5.09
21.59
7.27
10.41
60.73
63
f.
4 78
21_. 13
6.69
10.46
61.72
m.
f.
f.
One week
49
m.
11.96
23.06
7.27
12.88
56.79
46
m.
14.95
21.92
9.23
12.44
56.41
59
m.
9.55
25.03
8.90
11.62
54.45
60
f.
9.63
24.68
8.00
11.22
56.10
49
f.
10.33
23.54
9.37
11.13
55.96
46
f.
13.23
23.98
10.74
12.55
52.73
Three weeks
53b
m.
25.80
19.49
7.40
15.20
57.91
53b
m.
29.08
18.97
10.94
15.37
54.72
53b
m.
29.89
18.24
9.50
14.27
57.99
57
f.
17.34
24.16
9.17
14.65
52.02
Six weeks
50a
m.
82.50
50a
f.
76.80
50a
f.
78.60
50a
f.'
78.80
11.25 12.15 11.82 11.97
Ten weeks
175.20 120.30 130.20
8.56
9.98
10.14
5.21 5.24 5.50
14.63 14.88 14.90 15.37
15.77 16.45 14.54
67.93 67.07 65.06 66.09
70.46 68.33 69.82
GROWTH OF THE ALBINO 1{.\T
455
TABLE l-ContlMu.-.l Fire nionthfi^
UTTER NUMBER
SEX
NET BODY WEIOHT
HEAD
per cent
8.35
10.00
9.92
UPPKK EXTRKMITY
LOWER EXTREMITY
TRUNK
28 28 37
m. f. f.
grams
239.40 171.50 161.30
per cent 5.43 6.01 6.17
per cent 14.91 15.80 16.20
per cent
71.31 68.19 67.71
One year
39
m.
229.20
9.10
4.93
14.62
71.35
37
m.
276.40
9.18
4.67
14.54
71.61
39
f.
161.10
9.60
4.68
14.73
70.99
1 The third individual in this group was 8 months old.
TABLE 2
Albino rat — Average percentage weight of head, trunk and extremities at various
ages (from table 1 )
AGE
HEAD
1 UPPER
EXTREMITY
LOWER EXTREMITY
TRUNK
per cent
per cent
per cent
per cent
Newborn
21.65 (23.43)1
7.39
9.45
61.51 (59.73)'
One week
23.70 (25.74)
8.92
11.97
55.41 (53.37)
Three weeks
20.22 (24.27)
9.25
14.87
55.66 (51.61)
Six weeks
11.80 (15.17)
6.72
14.94
66.54 (63.17)
Ten weeks
9.56 (11.21)
5.32
15.59
69.53 (67.83)
Five months
9.42 (10.47)
5.87
15.64
69.07 (68.02)
One year
9.29 (10.75)
1 4.76
14.63
71.32 (69.86)
1 Figures in parentheses indicate the average percentages of the head (and corresponding percentages of the trunk) in a much larger series, including 20 or more of each sex at each age.
It is thus a remarkable fact that for a short time after birth the head of the albino rat grows more rapidly than the remainder of the body, probablj' reaching its maximum relative size in the second week. It is well known that the head of animals in general IS relatively largest during early embryonic life, and that it declines during the later prenatal period (cf. Jackson). After birth, since it is still relatively large as compared with the adult, the head would naturally be expected to continue to decline in
456
C. M, JACKSON AND L. G. LOWREY
TABLE 3
Albino rat — Percentage weight of skin, skeleton, musculature and viscera
Newborn
LITTER NUMBER
SE^
NET BODY WEIGHT
SKIN
SKELETON
MUSCULATURE
VISCERA
REMAINDER
47
m.
grams
5.88
per cent
18.30
per cent
13.95
per cent 21.26
per cent
17.38
per cent
29.11
47
m.
5.96
16.90
15.61
22.56
19.00
25.93
47
m.
6.25
20.29
15.84
24.66
17.78
21.43
A22
m.
4.87
21.50
19.70
23.40
15.94
19.46
A23
m.
5.22
19.60
19.50
18.90
17.50
24.50
A24
m.
4.57
22.30
23.50
20.60
18.50
15.10
A34
m.
4.20
18.15
13.70
26.70
18.13
23.32
A34
m.
4.53
18.00
14.70
26.35
16.68
24.27
A34
m.
4.54
21.24
16.59
25.25
17.10
19.82
62
4.27
19.01
16.43
25.00
18.48
21.08
58
5.09
20.43
14.33
26.54
■ 18.21
20.49
63
4.78
19.46
16.50
27.85
19.68
1€\ 51
A25
4.44
21.00
20.40
21.30
20.17
17.15,
A29
3.58
21.20
24.80
23.90
19.86
10.24 ■<
A34
4.47
19.80
14.80
29.80
17.13
18.47
A34
4.17
17.65
15.74
24.42
18.17
24.02
A34
3.38
20.25
18.00
24.62
17.15
19.98
A34
4.26
20.37
16.80
25.60
18.02
19.21
One week
46
m.
14.95
29.36
15.78
22.41
17.43
15.02
49
m.
11.96
31.52
17.06
24.58
15.29
11.55
59
m.
9.55
25.23
17.49
24.60
19.68
13.00
A22
m.
10.30
29.90
22.20
22.50
19.92
5.48
A32
m.
8.99
23.96
17.70
22.53
18.61
17.20
A32
m.
10.76
25.45
18.90
19.25
20.13
16.27
M9
m.
8.11
24.10
19.40
23.70
20.98
11.82
M9
m.
9.12
23.50
18.60
23.50
20.42
13.98
46
13.23
29.37
14.36
24.35
18.26
13.66
49
10.33
31.75
15.30
26.52
15.55
10.88
60
9.63
25.34
17.54
24.00
18.55
14.87
A21
8.85
28.60
23.80
23.40
18.41
5.79
A24
7.65
24.20
23.60
19.00
20.63
12.57
A28
6.98
23.30
22.20
22.40
20.50
11.60
A32
8.76
21.30
16.10
19.60
19.80
23.20
A32
10.63
27.00
18.05
21.63
19.16
14.16
A33
I
8.07
21.78
18.52
22.47
20.09
17.14
A33
7.43
22.05
17.60
23.30
20.37
10.68
A33
9.95
23.96
16.70
23.90
20.46
14.98
GROWTH OF TIIK ALHINO ItAT
457
UTTER NTMUEH
5;ib 53b 53b
A32
M9
I\I9
M9
57 A26 A32 A32 A33 A33
50a A24 A24 A28 A29 A29
50a 50a 50a
A29
A29
A29
A31
A31
111. m. m. m. m. m. 111.
f. f. f. f. f. f.
NET BODV WEIGHT
grams
25.80 29.08 29.89 25.91 25.78 25.40 26.50
17.34 18.41 23.72 25.70 24.40 24.30
TABLE 3-Contlmu'.|
Three weeks
BKI.V SKELBTON
per cent 29.20 26.39 27.49 18.70 22.10 21.50 19.50
22.26 23.55 21 . 10 19.80 18.80 20.55
per cent 14.90
16.72 13.11 17.30 15.70 15.60 15.80
19.49 21.08 16.65 17.10 15.90 16.43
MU8CULATURB
per cent 29.80 28.08 27.69 27.10 26.70 26.30 28.30
30.22 20.14 25.66 27.50 25.30 26.77
24.82 20.57 21.90 20.91 20.09 20.35
Six weeks
m. m. m. m. m. m.
f. f. f. f. f. f.
82.5 54.1 41.5 56.6 62.9 62.9
76.8 78.6 78.8 54.7 59.8 64.8 64.7 62.7
25.86 20.00 20.20 19.80 17.90 17.63
25.53 24.94 25.55 16.74 21.00 19.10 19.70 18.84
11.67 15.15 20.10 14.70 14.16 14.31
10.50 12.63 11.82 14.13 13.60 13.40 14.15 15.35
35.13 29.60 26.10 33.70 34.90 34.45
28.56 33.77 35.25 33.82 34.60 33.90 31.42 32.60
20.80 20.37 21.79
20.78 21.47 22.89
18.35 19.22 18.41 21.27 19.98 19.72 20.41 20.01
I<GMAI.NI>KR
per cent
jyer cent
22.08
4.02
21.59
7.22
20.38
11.33
20.79
10.11
20.61
14.89
20.24
10.30
22.35
14.05
Ten weeks
3.21 14.66 14.69 14.69 19.91 15.90
6.54 14.88 11.81 11.02 11.57 10.72
17.06 9.44 8.97 14.04 10.92 13.88 14.32 13.20
50b
m.
175.2
20.95
11.07
43.15
16.15
8.68
A28
m.
109.2
1 15.60
12.00
39.60
17.57
15.23
A 28
m.
134.3
16.80
10.40
40.90
16.69
15.21
A30
m.
144.7
t 18.70
12.20
37.40
15.72
15.98
A30
m.
187.2
18.80
10.00
37.90
14.89
18.41
458
C, M. JACKSON AND L. G. LOWREY
TABLE 3— Continued
Ten weeks — Continued
LITTER NUMBER
SEX
NET BODY WEIGHT
SKIN
SKELETON
MUSCULATURE
VISCERA
REMAINDER
grams
per cent
per cent
per cent
per cent
per cent
50b
120.3
22.28
12.39
49.13
14.97
1.23
50b
130.2
21.34
12.90
41.78
15.75
8.23
A26
109.9
17.93
11.70
41.42
16.32
12.63
A28
108.4
16.70
12.20
42.30
14.99
13.81
A29
122.2
17.80
11.90
37.80
17.22
15.28
Five months^
28
m.
239.4
22.76
13.24
41.39
15.39
7.22
A22
m.
192.3
18.80
12.30
42.10
12.99
13.81
A26
m.
203.4
18.50
10.40
43.90
13.26
13.94
A26
m.
232.4
18.90
10.00
43.10
13.42
14.58
A26
m.
195.4
18.30
10.20
41.20
14.02
16.28
A26
m.
249.4
18.00
9.37
44.30
13.13
15.20
37
f.
161.3
20.36
10.54
46.50
12.53
10.07
28 f.
171.5
17.79
14.58
46.25
14.53
6.85
A22 f.
157.1
18.80
11.60
40.20
16.19
13.21
A22 f.
158.0
16.20
12.20
39.70
15.46
16.44
A22
f.
158.5
15.70
10.90
41.90
17.24
14.26
A22
f.
128.2
14.50
11.80
41.90
18.70
13.1.0
A26
f.
149.0
17.20
12.90
41.90
15.21
12.79
One
year'^
39
m.
229.2
15.93
9.69
46.51
14.86
13.01
37
m.
276.4
20.62
11.61
42.65
13.63
11.49
A—
m.
253.5
18.45
10.45
46.33
11.49
13.28
A—
m.
281.6
13.75
7.35
50.50
12.17
16.23
39
f.
161.1
21.97
10.86
41.15
13.85
12.17
3
f.
206.0
16.99
15.53
45.46
13.82
8.20
1 The first female of the 5 months' list was 8 months old. The age of the third and fourth males of the year list was not exactly known, but it was in the neighborhood of a year.
(iKOW ril OF TlIK ALIUNO IJAT 459
relative size, imd we meet no data or statements to the contrary in the Hterature. \\'hether this early postnatal acceleration of the head growth is peculiar to the rat is therefore unknown, as well as its relations to prenatal f2;rowtli.
It is interesting to note that the maximum relative weight of the head of the young rat (about 26 per cent) is nearly the same as that observed by Jackson for the human newborn; and that the adult rat head (9 to 10 per cent) is also not far from that of the human (6 to 10 per cent) as given by Meeh and Harless. Few data are available for comparison with other forms. Martiny, in 3 groups of beef cattle (10 in each group), finds the head forming an average of 2.7 per cent to 2.9 per cent of the body weight. Lawes and Gilbert give data showing the head in 2 fat calves to average 5.5 per cent of the body weight; and in 16 adult heifers and steers, 2.7 per cent. In 249 sheep they find the head averages 2.9 per cent of the body, varying from 3.6 per cent in 5 thin yearlings to 2.5 per cent in 45 very fat sheep, aged If years. Lowrey finds that in the pig the head decreases from about 22.3 per cent (late fetus) to an average of 6.3 per cent in the adult.
2. Extremities (tables 1, 2, 5; fig. 1). In spite of individual variations shown in table 1, the upper extremities on the average (table 2, fig. 1) are seen to increase from 7.39 per cent of the body at birth to 8.92 per cent at 1 week, and to 9.25 per cent at 3 weeks. From this maximum relative size, they decrease rapidly to 6.72 per cent at 6 w^eeks, and thereafter more slowly to an average of 4.76 per cent at 1 year.
The lower extremities show a continuous relative increase, w^hich is at first more rapid, from an average of 9.45 per cent at birth to 11.97 per cent at 1 week, and to 14.87 per cent at 3 weeks. Thereafter the increase is slower, reaching a maximum of 15.64 per cent at 5 months, with an apparent later slight decrease to 14.63 per cent at 1 year.
The number of observations is insufficient to show any difference between the sexes as to relative weight of the extremities, if such exists. Similarly, the data on the gray rat (table 5) reveal no significant difference from the albino.
460
C. M. JACKSON AND L. G. LOWREY
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(iltOWni OK THE ALHINO 1{AT
461
Seurcely any data are found in the literature as a basis for comparison with other forms. The observations made upon domestic animals at the various agricultural experiment stations usually follow the 'butcher's cuts/ which unfortunately do not correspond to the anatomical subdivisions. The only data available are the observations by Jackson, Meeh and Harless (1. c), which indicate that in the human newborn the upper extremities form about 10 per cent of the body, which is about the same as in the adult; and that the lower extremities form about 20 per cent in the newborn and about 35 per cent in the adult. Thus, as might be expected, the extremities, especially the lower, are relatively much larger in man than in the rat. No observations are recorded for stages between the newborn and the adult.
TABLE 5
Gray (brown) rat — Percentage weight of head,
trunk and extremities
SEX
NET BODY WEIGHT
„_, . „ UPPER °^^° EXTREMITY
LOWER EXTREMITY
TRUNK
m.
grams
65.0
per cent per cent
14.66 5.95
per cent
13.88
per cent
65.51
m.
95.4
12.17 5.83
15.34
66.66
f.
107.5
10.18 j 5.58
15.81
68.43
m.
164.0
9.27 5.24
14.94
70.55
f.
254.01
7.85 5.02
13.68
73.45
1 Including gravid uterus, which weighed 13.76 grams.
3. Trunk (tables 1, 2, 5; fig. 1). The trunk weight w^as estimated by subtracting the weight of the head and extremities from the net body weight. The loss of blood (which was usually comparatively small) therefore falls entirely to the trunk. In the parentheses in table 2 are given the figures for the trunk corresponding to the larger series, as explained for the head, and these are also utilized for the diagram in figure 1. It is evident that both sets agree in showing that the trunk decreases notably in relative size from about 60 per cent of the body at birth to a minimum (52 to 55 per cent) at the first to third weeks (corresponding to the relative increase of the head and extremities), and thereafter increases steadily, reaching its maximum relative size (about 70 per cent) in the oldest and largest animals observed.
462 C. M. JACKSON AND L, G. LOWREY
No differences are evident on comparing the sexes, or the data for the gray rat (table 5) . The only data found in the literature for comparison with other forms are again those of Jackson and IVIeeh (1. c), which show that the trunk forms about 45 per cent of the body in the human newborn, and about 48 per cent in the adult. Thus the human trunk is relatively smaller, corresponding to the relatively larger extremities.
As Jackson has pointed out for the human body, it may likewise be noted in the rat that the intensity of growth seems to pass over the body somewhat like a wave, reaching its maximum first in the head and upper extremity, and later passing backward along the trunk to the abdominal portion and lower extremity. This relation is evident in figure 1. It is furthermore evident from this figure that the adult relations of the component parts of the body have practically been reached at 10 weeks. The only changes apparent thereafter are a very slight relative increase in the trunk, compensated by a corresponding decrease in the head and extremities.
RELATIVE GROWTH OF THE VARIOUS SYSTEMS
1. Skin (tables 3, 4, 6; fig, 2). As shown by table 4 and in figure 2, the integument (including claws and adherent subcutaneous tissue) grows with remarkable rapidity during the first week, the average increasing from 19.75 per cent to 25.88 per cent of the whole body. The numbers at each age are too large and the uniformity too great to account for this on the score of possible individual variations. This unquestionable increase is however somewhat difficult to explain. It is not due to the development of the hair coat, for this does not become well developed until the second and third weeks. Neither is it apparently due to any unusual accumulation of fat in the subcutaneous tissue.
Fig. 2 Change in the percentage weight of the various systems of the albino rat. The width (in the vertical direction) of each strip is proportional to the percentage weight of the corresponding system. The percentage weight is indicated for every system at each of the ages. Up to the age of 10 weeks (that is, in the ruled portion of the figure), the horizontal distance is drawn to scale, jjroportional tf) the age. Beyond 10 weeks, the horizontal distance is not in proportion to the age.
463
464
C. M. JACKSON AND L. G. LOWREY
After the first week the skin decreases in relative weight, at first more rapidly, and later more slowly, reaching an average of a little less than 18 per cent at 1 year. There are no noteworthy differences apparent between the sexes, or in the gray rat (table 6) ,
Numerous observations upon the integument in other forms are available for comparison, though chiefly for the adult. According to Vierordt, the average for the human newborn is 19.7 per cent; for the adult, 17.8 per cent. Welcker and Brandt record observations upon a large number of species, including besides mammals many birds (14 to 28 per cent), reptiles (6 to
TABLE 6
Gray {brown) rat — Percentage weight of skin, skeleton, musculature, viscera and
remainder
SEX
NET BODY WEIGHT
SKIN
SKELETON
MDSCaLATURE
VISCERA
REMAINDER
groTns
per cent
per cent
per cent
per cent
per cent
m.
65.0
18.42
13.15
35.39
23.40
9.64
m.
95.4
19.29
13.85
38.57
23.21
5.08
f.
107.5
20.37
13.86
42.14
17.51
6.12
m.
164.0
17.35
13.29
41.66
20.95
6.75
f.
254.01
19.41
10.16
44.21
16.22
10.00
1 Including gravid uterus, which weighed 13.76 grams.
21 per cent), amphibia (13 to 21 per cent), and fishes (5 to 13 per cent). These differ so widely in the structure of the integument (especially the appendages), however, that their relative weights are scarcely comparable with each other or with those of mammals. This is also true to a certain extent even for the various mammals. Of mammals, Welcker and Brandt give data for the relative weight of the integument as follows : shrew mouse (Sorex), young, 33.3 per cent, adult, 14 per cent; mouse, 17.6 per cent; bat, 19.5 per cent; mole, 20.2 per cent; hedgehog, 24.3 per cent; guinea pig, 19.8 per cent; monkey, 10.4 per cent; seal, 19.6 per cent; elephant, 13.1 per cent. Sedlmair finds the skin of a well-nourished cat forms 14.7 per cent of the body weight; and Weiske, for rabbits, 14.3 to 16.2 per cent. For dogs (Dachshund), Falck finds the average in 4 newborn 21.8 per cent; at 72 days,
GHOW rn OF THE ALBINO HAT 465
25.4 per cent; 70 days, 18.8 per cent; 108 dnj^s, 10. G per eent; 113 days, 21.3 per cent.
For cattle and sheep numerous data are available. Lawes and Gilbert for 2 fat calves (9 to 10 weeks) find the hide averages 0.9 per cent of the bodj weight; for 16 adult cattle, 7.5 per cent. JMartinj' in 3 groups (10 each) of beef cattle found the average 7.8 per cent, 9.1 per cent and 8.0 per cent, respectively. For sheep. Lawes and Gilbert find in a fat lamb (6 months), the integument forms 9.6 per cent (skin proper, 5.9 per cent, wool, 3.7 per cent) ; in adults, the average of 249 sheep was 11.7 per cent, ranging from 14.1 per cent (in 5 thin yearlings) to 10.5 per cent (45 very fat adults, If years). Henneberg in 19 sheep finds the skin forming 7.1 per cent to 12.5 per cent. Long in 2 fat sows finds the skin (without fat) to form 4.9 per cent and 5.1 per cent.
The foregoing data are reckoned in percentage of the net body weight, excluding contents of the alimentary canal. Voit has pointed out further that if the state of bodily nutrition, the amount of fat and hair, etc., present are taken into account, the variations in percentage weight of the body for the different organs are much less. Thus in 6 dogs, the skin varied from 8 per cent to 19 per cent of the body weight; but reckoned on the fat-free, hair-free basis, the variation was only from 7 per cent to 9 per cent for the well-nourished, and from 7 per cent to 13 per cent for the poorly-nourished animals.
The relative weight of the skin in the rat is thus high as compared with that of most mammals. In general, the skin evidently forms a relatively larger percentage of the body weight in small animals, which is to be expected, since in these the surface area is larger in proportion to the mass of the body.
Skeleton (tables 3, 4, 6; fig. 2). The skeleton (including bones, cartilages and ligaments) like the skin, apparently increases relatively for a short time after birth, the average percentage being 17.27 per cent at birth, and 18.47 per cent at 1 week (table 4, fig. 2). Thereafter it diminishes steadily at the various ages studied, reaching an average of 10.91 per cent at 1 year. The high figure for one of the females at 1 year (15.53 per cent) is probably either an error or an abnormality. There are no constant differences
THE ANATOMICAL RECOBD, VOL. 6, NO. 12
466 C. M. JACKSON AND L. G. LOWEEY
apparent between the sexes, and the hmited data for the grayrat (table 6) are well within the limits of variation for the albino.
Of data available for comparison with other forms, Vierordt estimates the skeleton in the human newborn at 13.7 per cent; in the adult, 17.5 per cent. Miihlmann estimated that the human skeleton increases from 12.6 per cent in the newborn to a maximum of 20.4 per cent at 11 to 20 years, thereafter decreasing to 10.1 per cent in old age.
Welcker and Brandt in addition to numerous data for the skeleton of birds (7 to 13 per cent), reptiles (7 to 43 per cent), amphibia (7 to 10 per cent), and fishes (6 to 17 per cent), give the following for mammals: mouse, 8.4 per cent; bat, 14.6 per cent; hedgehog, 11.1 per cent; guinea pig, 8.8 per cent; seal, 11.1 per cent; monkey, 16.8 per cent; elephant (skeleton plus musculature), 69.7 per cent. Falck for Dachshund, newborn (average of 4), 14.4 per cent; nearly grown, 14.9 per cent; adult, 14.0 per cent. Sedlmair, for well-nourished cat, finds 10.1 per cent; Weiske, for rabbits, 8.1 per cent to 9.2 per cent.
Martiny, in 3 groups (10 each) of beef cattle, finds the skeleton averages 14. 3 per cent, 14.6per cent and 15.3per cent, respectively. Henneberg gives average of 2 lambs, 10.4 per cent; and of 8 adult sheep, 4.4 per cent to 7.1 per cent, being least in the fattest animals. Long, for 2 fat sows, gives 6.3 per cent and 6.7 per cent.
An inspection of the data given above shows great variation in the relative weight of the skeleton, even in animals close together in size and relationship. This is due partly to differences in skeletal structure and in the amount of musculature (with which the skeletal system is to a certain extent correlated) and partly to variation in the state of bodily nutrition. Voit shows, for instance, that among dogs whose skeleton varied from 12 per cent to 29 per cent of the body weight (as ordinarily reckoned) , if reckoned upon a fat-free, hair-free basis the percentage weight varies from 14 per cent to 15 per cent in well-nourished, and from 17 per cent to 30 per cent in poorly-nourished animals.
Musculature (tables 3, 4, 6; fig. 2). Unlike the skin and skeleton, the musculature (including tendons) appears to decrease slightl}^ in relative weight, from an average of 24.37 per cent to
CKOWTH OF THE ALHIXO KAT 467
22. (S2 por cent during the first week (table 4, fig. 2). Thereufter it iuereiises steadily in relative weight, reaching an average of 45.43 per cent at 1 year. No noteworthy difierences api)ear between the sexes, or in the gray rat (table 6).
The musculature forms so large a mass that its growth virtually dominates the bod}'. Thus during the first week, when the musculature lags behind in growth, the other constituents push ahead and increase their relative weights. Later, however, when the musculature assumes its characteristic more rapid rate of growth, it forges ahead and the other constituents necessarily decrease steadily in relative weight up to the adult condition. The increase in the relative proportion of the musculature between the newborn and the adult is also characteristic. of man, and perhaps to a shghter extent in other animals. No data are available to show whether there is in any other species a temporary decrease after birth as shown above for the rat. .
For the human newborn, Welcker and Brandt cite 2 cases from BischofT in which the musculature formed 23.3 per cent and 24 per cent of the body. Vierordt estimates for the human newborn, average, 25 per cent, and for the adult, 43.2 per cent. Miihlmann for newborn estimates 22.4 per cent, increasing to 43.2 per cent at 41 to 50 years, thereafter decreasing to 18.6 per cent in old age.
Welcker and Brandt, in addition to numerous birds (36 to 55 per cent), reptiles (19 to 57 per cent), amphibia (43 to 54 per cent), and fishes (49 to 59 per cent), give the following for the musculature of mammals: bat, 41.6 per cent; mouse, 43.4 per cent; hedgehog, 36.6 per cent; guinea pig, 45.8 per cent; monkey, 53.5 per cent; elephant (skeleton plus musculature), 69.7 per cent; ox (skeleton plus musculature), 64 per cent; deducting 15 per cent for skeleton (Martiny) gives 49 per cent. Falck, for Dachshund, finds in newborn, average, 36.2 per cent; nearly grown, 38.4 per cent; adult, 39.6 per cent. Sedlmair, for cat, finds 57.2 per cent; and Weiske, for rabbits, 49.7 to 57.2 per cent. Lawes and Gilbert, in a lean pig, find 41.6 per cent for muscle, and in a fat pig, 30.9 per cent. Long, in 2 fat sows, finds 29.7 per cent and 32.6 per cent. Henneberg, in 2 lambs, finds the average 34.4 per
468 C. M. JACKSON AND L. G. LOWREY
cent ; in 8 adults, 20.3 per cent to 33.2 per cent, the lower percentage corresponding to the fatter animals.
Voit, in the 6 dogs previously mentioned, finds the musculature forming 36 per cent to 49 per cent of the body weight. Reckoned on a fat-free, hair-free basis, however, the variation is only 52 to 55 per cent for well-nourished, and 40 to 48 per cent for poorlynourished animals.
Thus in comparison with other animals with respect to the relative weight of the musculature, the rat occupies an intermediate position. In most adult mammals, the musculature forms between 40 per cent and 50 per cent of the body weight. Theoretically^, as Welcker has noted, a larger relative weight of muscle might be expected in a larger animal. This is because the functional capacity (tension strength) of a muscle varies as the crosssectional area, which would increase only in proportion to the square of a li^iear dimension, while the mass of the body to be supported and moved would increase as the cube of the same dimension. The data do not seem to confirm this theory, however. For example, the percentage of muscle is nearly the same in the mouse as in the elephant. Among mammals, the largest percentages of muscle recorded are in comparatively small animals (rabbit, cat), while the smallest relative weights are found in comparatively large animals (pig, sheep).
4- Viscera (tables 3, 4, 6; fig. 2). Like the skin and skeleton, the visceral group (including the central nerv^ous system, thoracic and abdominal viscera) increases in relative weight immediately after birth. In the newborn, it averages 18.05 per cent, increasing to 19.17 per cent at 1 week, and continuing to increase to a maximum of 21.28 per cent average at 3 weeks. Thereafter it diminishes gradually in relative weight, reaching an average of 13.3 per cent at 1 year. There are no evident differences between the sexes. The data for the gray rat (table 6) appear constantly higher than those for the albino of corresponding body weight. Whether this is really a constant difference is somewhat doubtful, however, on account of the small number of observations on the gray rat.
GROWTH OK THE AIJU.NO HAT 469
The visceral jj;r()up in the Iuuikui lunvboni averages about 24 per cent of the body weight (Jackson). According to Vierordt, it forms 23.4 per cent in tlie newborn, decreasing to 9.8 per cent in the adult. Accurate data for comparison of the intermediate stages are not available for man or for any other animal. In the pig, Lowrey finds about 16 ])er cent for the newborn, and 7.8 per cent for the adult. A smaller decrease between newborn and adult (21.8 per cent to 19.5 per cent) is shown by Falck's data for the dog.
Welcker and Brandt, in addition to data for various birds, reptiles, amphibia and fishes, give data from which the following have been calculated for mammals: bat, 19.5 per cent; shrew mouse, 3'oung, 21.1 per cent, adult (includes intestinal contents?), 31.7 per cent; mouse, 22.3 per cent; guinea pig, 17.6 per cent; hare, 16.3 per cent; sheep, 11.5 per cent; monkey, 12.8 per cent; ox, 10.3 per cent; elephant, 12.5 per cent. Sedlmair, for cat, finds 14.5 per cent; and Baumeister for adult pig, in medium condition, 6.0 per cent, fat, 9.8 per cent.
Voit, in the 6 dogs before mentioned, finds the visceral group forming 17 per cent to 22 per cent of the body. (Viscera in this case mclude blood, but not heart). When calculated on 'be fatfree, hair-free basis, however, unlike what was found for skin, skeleton and musculature, the variation scarcely appears less. In well-nourished animals, it was found to be 19 per cent to 22 per cent, and in the poorly-nourished, 17 per cent to 25 per cent.
In general, the smaller mammals have a relatively larger visceral apparatus, probably correlated with, a more intense metabolism. The rat occupies a somewhat intermediate position, the relative weight of the viscera being less than that of most of the small mammals, but greater than that of the larger mammals.
5. Remainder (tables 3, 4, 6; fig. 2). The remainder is the amount obtained by subtracting from the net body weight the weight of the skin, skeleton, musculature and visceral group. In addition to the liquids escaping from the tissues and body cavities and the loss by evaporation, it includes a few small unweighed organs (genitaha, aside from gonads, larynx, trachea,
470 CM. JACKSON AND L. G. LOWREY
pharynx, oesophagus, large vessels) and varying amounts of fat in connection with the muscles and abdominal cavity.
It will be noted (table 4, fig. 2) that in the newborn the remainder forms a considerable proportion of the body (average 20.56 per cent) . It decreases, at first very rapidly, reaching an average of 13.68 per cent at 1 week, and then more slowly to 12.85 per cent at 3 weeks. From this time onward, it remains on the average rather constant, between 12 per cent and 13 per cent, but with considerable individual variation, due chiefly to the varying amounts of fat present. There is no evident variation according to sex; but in the gray rat the remainder appears low (table 6), probably because there is usually less fat present.
The remarkable decrease in the remainder during the first week naturally calls for an explanation. It cannot be due to varying amounts of fat, for no appreciable amount is visible at that age. There is likewise no considerable variation in the small organs included in the remainder. The decrease is apparently to be explained as follows. The newborn rat is very "juicy," or rich in water, with relatively large amounts of liquid in the interstitial tissue spaces as well as in the various cavities of the body. This excess of liquid largely disappears during the first week, and the remainder is thereby very markedly diminished.
In the human newborn, the remainder is apparently not more than 15 per cent. Vierordt's data give a remainder of about 18.1 per cent for the newborn, and 11.6 per cent for the adult. This, however, includes the intestinal contents. There is evidently a decline somewhere between the newborn and the adult, but data upon the intermediate stages are lacking. In the dog, as shown by Falck's data, the remainder is apparently about the same in the newborn (5.8 per cent) as in the adult (5.7 per cent). In a well-nourished cat, the remainder forms 3.5 per cent (Sedlmair). From data by Welcker and Brandt, remainders were calculated as follows: ox, 17.6 per cent; sheep, 14.5 per cent; mouse, 10.3 per cent; guinea pig, 7.9 per cent; hare, 7.2 per cent; monkey, 6.5 per cent; elephant, 4.8 per cent. The high proportion in the ox and sheep is due to their excess of body fat, and, as in the case
GROWTH OF THE ALBINO RAT 471
of tlio nit, variations in the adults of other animals are apparently duv chiefly to difierenee in this respect.
In i-e«!;anl to the relative size of the various systems, as already mentioned for the component parts, practically the adult relations have been reached at the age of 10 weeks. This is evident from figure 2, but would appear still more striking if the horizontal distance beyond 10 weeks were increased to scale in proportion to the length of time up to 1 year. The only change of note after 10 weeks is the slight relative increase in the musculature, which is balanced by a decrease in the other systems, chiefly in the viscera.
CONCLUSIONS
The more important conclusions may be summarized briefly as follows:
1. The head of the albino rat increases in relative weight from an average of about 23 per cent of the body in the newborn to nearly 26 per cent at 1 week. Thereafter it decreases in relative size, forming about 10 per cent of the body in the adult rat (age, 1 year).
2. The upper extremities increase from about 7 per cent of the body in the newborn rat to about 9 per cent at 3 weeks, thereafter decreasing to less than 5 per cent at 1 year. The lower extremities increase steadily from about 9 per cent at birth to about 15 per cent at 1 year.
3. The trunk decreases from an average of about 60 per cent of the body at birth to about 52 per cent at 3 weeks, increasing thereafter to about 70 per cent at 1 year.
4. JThe skin increases rapidly from about 20 per cent of the body in the newborn to nearly 26 per cent at 1 week j^ thereafter it decreases steadily to about 18 per cen t at 1 year. ~^
5. The skeleton increases slightly from an average of about 17 per cent of the body in the newborn to about 18 per cent at 1 week; thereafter it decreases steadily in relative weight, to about 10 per cent in the adult.
6. The musculature decreases relatively from an average of 24.4 per cent of the body in the newborn to 22.8 per cent at 1
472 CM. JACKSON AND L. G. LOWREY
week; thereafter it increases steadily, averaging slightly more than 45 per cent of the body in the adult rat.
7. The visceral group increases from an average of 18 per cent of the body in the newborn to about 21 per cent at 3 weeks; thereafter decreasing to nearly 13 per cent at 1 year.
8. The remainder (net body weight minus skin, skeleton, musculature and viscera) undergoes a striking decrease from an average of about 21 per cent of the body at birth to about 14 per cent at 1 week. This is due to the disappearance of excessive liquids in the newborn. After 3 weeks, the remainder averages slightly more than 12 per cent of the body.
9. The body of the- albino rat has practically reached the adult proportions in its component parts and systems at the age of 10 weeks.
10. The data indicate no noteworthy differences between the sexes in the relative weight of the various parts and systems. With the possible exception of slightly heavier viscera and smaller remainder, the few data on the gray rat likewise reveal no marked difference in this form.
GROWTH OF TMIO ALBINO RAT 473
BlBl.lOCIUArjIY
Baumeister, W. 1S90 Anleitung ziir Hchwcinezuclit und Schweinehaltung. 5 Aufl. Berlin.
Falck, C. Ph. 1S54 Beitriige zur Kenntniss der Wuchstumsges'chichte des Tierkorpcrs. Archiv. fiir path. Anat. (Virchovv's), Bd. 7.
Harless 1876 Lehrbuch der plastischen Anatomie. 2 Aufl. (cited by Vierordt)
Henneberg, W. 1878, 1880 Journal fiir Landwirtschaft. (Cited by Vinson, Beitriige zur Methodik der Analyse ganzer Tierkorper. Inaug. Dissert. Gottingen, 1904.) See also Referat von W. Henneberg, Ueber Fleischuud Fettproduction in verschiedenem Alter und bei verschiedener Ernahrung. (Nach Versuehen mit Schafen, auf der Versuchs-station Gottingen-Weende von Dr. E. Kern und Dr. H. Wattenberg ausgefiihrt.) Zeitschr. fiir Biologie, Bd. 17.
Jackson, C. M. 1909 On the prenatal growth of the human body and the relative growth of the various organs and parts. Am. Jour. Anat., vol. 9.
Lawes and Gilbert. 1859 Experimental inquiry into the composition of some of the animals fed and slaughtered as human food. Philos. Trans. Royal Soc, London, pt. 2.
Long, James 1906 The book of the pig. 2 Ed., London and New York.
Lowret, L. G. 1911 Prenatal growth of the pig. Am. Jour. Anat., vol. 12.
Martiny (date?) Arbeiten der deutschen Landwirts-Gesellschaft, H. 18. (Cited by Vinson, Beitrage zur Alethodik der Analyse ganzer Tierkorper. Inaug. Dissert. Gottingen, 1904.)
Meeh, Carl 1895 Volummessungen des menschlichen Korpers und seiner einzelnen Theile in den verschiedenen Altersstufen. Zeitschrift fiir Biologie, Bd. 31.
MtJHLMANN, M. 1900 Ueber die L'rsache des Alters. Wiesbaden.
Sedlmair, a. C. 1899 Ueber die Abnahme der Organe insbesondere der Knochen beim Hunger. Zeitschrift fiir Biologie, Bd. 37.
Vierordt, H. 1906 Anatomische, phj'siologische und physikalische Daten und Tabellen. 3 Aufl. Jena.
VoiT, Erwix 1905 Welchen Schwankungen unterliegt das Verhaltnis der Organgewichte zum Gesamtgewicht des Tieres? Zeitschrift fiir Biologie, Bd. 36.
474 C. M. JACKSON AND L. G. LOWREY
Weiske, H. 1895 Weitere Beitrage zur Frage liber die Wirkung eines Futters mit sauren Eigenschaften auf den Organismus, insbesondere auf das Skelett. Zeitschrift fur physiologische Chemie, Bd. 20.
Welcker und Brandt. 1903 Gewichtswerte der Korperorgane bei dem Menschen und den Tieren. Archiv fiir Anthropologic, Bd. 28.
Duplication of the inferior vena cava in man
MAURICE H. GIVENS
From the Department of Anatomy, Cornell University Medical College, Ithaca,
New York
TWO FIGURES
The two cases of duplication of the inferior vena cava described below were found in the dissecting room of the Cornell Universitj jNIedical College at Ithaca.
The first case occurred in a colored male, aged forty-seven, who died of general paresis, cadaver no. 466 of the Cornell series.
The common iliac veins of both sides are formed in the usual way by the junction of the external and internal ihacs. The right common ihac vein after a course of 4.5 cm. is joined not by the whole of the left common iUac but only by a large branch from it, the ramus communicans. The right inferior vena cava thus formed extends for a distance of 11 cm. as a large independent stem and is then joined by the left inferior vena cava and then forms the common vena cava and runs superiorly as a single trunk for 2.5 cm. when it enters the fossa for the vena cava in the hver and continues to the heart. The right common ihac vein begins at the level of the anterior superior ihac spine. It receives the ramus communicans at the superior border of the 5th lumbar vertebra and is joined by the left inferior vena cava at the inferior border of the first lumbar vertebra.
The left common ihac vein runs superiorly for a distance of 2 cm. when it divides into two branches of about equal size. The one mentioned above as the ramus communicans passes obliquely across the body of the 5th lumbar vertebra to join the right inferior vena cava. The other branch which represents
475
476 MAURICE H. GIVENS
the left inferior vena cava continues superiorly along the spinal column lateral to the aorta and nearly parallel to the right inferior vena cava. At the inferior border of the first lumbar vertebra where the lumbar veins enter it bends abruptly to the right and passes ventral to the aorta to join the inferior vena cava. The transverse part of it corresponds in position with the renal vein in a normal case.
An idea of the relative size of the different vessels is obtained from the following measurements which, in all cases, were made upon empty flattened vessels since all the vessels could not be fully distended:
Right inferior vena cava 3.0 cm.
Left inferior vena cava 1-6
Right common iliac vein 2.5
Left common iliac vein 2.0
Ramus communicans 1-7
The right inferior vena cava opposite the point where the left joins it receives three renal vems of 1.2, 0.6, and 0.7 cm. in diameter, the superior being the largest, and receiving the right suprarenal vein. The right inferior vena cava receives four lumbar veins.
The left inferior vena cava opposite its junction with the right receives five separate veins. Of these the most superior is the left suprarenal which is about twice as large as the right suprarenal. Tliree receive blood from the kidney. The most ventral is the largest renal vein, being 1.2 cm. in diameter, while the other two renal veins are over 0.3 and 0.6 cm. in diameter. The most posterior, a vein 0.6 cm. in diameter, is the left ascending lumbar vein. Its continuation is the hemiazygos (vena azygos minor). It receives a small anastomosing branch from the azygos vein (vena azygos major) 3 cm. before its junction with the left inferior vena cava. The left inferior vena cava receives, in addition to the ascending, two other lumbar veins, one 2 cm. inferior to the left ascending lumbar vein and the other 1 cm. superior to the beginning of the ramus communicans.
The right speniiatic vein empties at the junction of the right and left inferior venae cavae. The left spermatic vein joins the
DUPLICATION OF INFERIOR VENA CAVA
477
left, inferior vena cava; 5 cm. inferior to the entrance of the large anterior renal vein (fig. 1).
In the fall of 1911 a condition similar to the first was found in another subject (no. 401, Cornell series), a white male, aged fifty, who died of cirrhosis of the liver.
On the right the external iliac vein is joined at the level of the anterior superior iliac spine by the internal iliac vein to form the
AZYGOS
ANASTOMOSING
BRANCH RIGHT SUPRARENAL
RENALS RIGHT SPERMATIC
RIGHT INFERIOR VENA CAVA
RIGHT COMMON ILIAC
RIGHT EXTERNAL ILIAC
RIGHT INTERNAL ILIAC
HEMIAZYGOS
ASCENDING LUMBAR
LEFT SUPRARENAL
RENALS
-LEFT SPERMATIC
LEFT INFERIOR VENA CAVA
RAMUS COMMUNICANS •-LEFT COMMON ILIAC
LEFT
EXTERNAL ILIAC
__LEFT
NTERNAL ILIAC
Fig. 1 Semi-diagrammatic drawing of the venae cavae of subject no. 466.
right common ihac vein. The right common iUac vein then extends superiorly to a level corresponding to a plane, passmg through the lower quarter of the right kidney, where it is joined by the left common iliac vein to form the vena cava. From this point the inferior vena cava extends superiorly foi a distance of 2.5 cm. It then receives two large renal veins: one from each kidney, and extends in the usual way to the heart.
478 MAURICE H. GIVENS
The left internal and external iliac veins join at a level slightly lower than the right to form the left common iliac vein. This is joined 4 cm. from its origin by a small branch which connects it with the right internal iliac vein and it then extends 10 cm. farther superiorly to join the right as already noted.
On the left side it is quite evident that the vessel superior to the branch which connects with the right side should be considered a left inferior vena cava and it is worthy of note that it is a larger vessel than the corresponding vessel on the other side. On the right side it is not quite so clear where we should consider the inferior vena cava as beginning since the ramus communicans connects with the right internal iliac and not as is usually the case with the common iliac vein. This branch is quite small, measuring 2 or 3 mm. in diameter when flattened out. It receives the middle sacral vein.
The left common iliac vein, 2 cm. before its junction with the right, receives the right spermatic vein. The left renal vein receives the left spermatic vein.
There are a number of loops formed in the veins. A large branch joins the right external iliac vein, the right internal iliac vein forming a loop which encloses the external iliac artery. This loop receives the right superior gluteal vein and another small vein. The right common iliac vein about the middle of its course gives off a short branch which runs for 1.5 cm. and again joins the right common iliac vein forming a loop which receives a small lumbar vein (not shown in the figure).
The left external iliac vein gives off a small branch which joins the left internal ihac vein about 2 cm. before their junction. This loop is smaller than that of the other side and the artery does not pass through it. There is, however, another loop formed by the left internal iliac vein opposite the point where the left superior gluteal vein joins it. This encloses the left internal iliac artery.
I have been able to find reports of but 14 similar cases and for comparison will give a brief resume of them. They have been divided into two groups; those in which the left inferior vena cava is connected by anastomoses with the right and those in which it is not.
DUPLICATION OF INFERIOR VENA CAVA
479
Cafics with no anastomoses between the two cavae
In Kolhnan's ease in an adult, the right vena eava was 15 cm. long from junction of external and internal iliac and received the right renal vein: while tlie left vena cava was 17 cm. long and received the left renal vein. The two venae cavae joined to form a single vein which connected with the heart, and which was 10 cm. long from heart to the level of the superior mesenteric artery.
RIGHT SUPRARENAL RIGHT RENAL li,,,^^
RIGHT SPERMATIC
RIGHT INFERIOR VENA CAVA
RIGHT COMMON ILIAC
RIGHT INTERNAL
ILIAC RIGHT EXTERNALI
ILIAC
/t_- LEFT SUPRARENAL
LEFT RENAL
LEFT SPERMATIC
LEFT INFERIOR VENA CAVA
RAMUS COMMUNICANS
LEFT COMMON
ILIAC
f\\ LEFT INTERNAL
tj-\ ILIAC
LEFT EXTERNAL LI AC
Fig. 2 Semi-diagrammatic drawing of the venae cavae of subject no. 401. M, middle sacral vein; L, lateral sacral vein; G, superior gluteal vein.
Zaaijer reports a case in a male sixty-two years old in w^hich the inferior vena cava was normal but there was a branch parallel to the aorta establishing a communication between the left common iliac vein and left renal vein. This undoubtedly should be considered a left inferior vena cava. It is interesting to note that there was no right kidney in this case.
Flesch describes a case in which the left internal iliac vein passes superiorly along the aorta to join the left renal vein forming with this a
480 MAURICE H. GIVENS
single vessel which crossed the aorta at the level of the second lumbar vertebra, to join the right inferior vena cava. The azygos and hemiazygos veins remained normal.
In one of Nicolai's cases there was no anastomosis between the two cavae and each received tributaries from the corresponding side of the body. The right vena cava was normal to the lower half of the liver, where it joined with the vena cava from the left side. The left vena cava arose at the same level as the right and passed superiorly on the left of the aorta to the level of the hilus of the kidney, where it received the left renal vein and then ran over to the right to join the right vena cava opposite the point where this latter received the right renal vein. Each inferior vena cava was 5 cm. in diameter at the point of junction. The left suprarenal vein opened into this oblique portion of the left renal vein. The common trunk was 4.5 cm. long, and 2.5 cm. broad. Each of the separate inferior cavae received a spermatic and also lumbar veins.
Broca very briefly describes a case by Zagorsky in which the two primitive common iliac veins joined at the level of the articulation of the 1st and 2d lumbar vertebrae. Each of these received its corresponding renal, spermatic and lumbar veins, hence we must conclude that it is a case of double inferior vena cava.
Cases with anastomoses between the two venae cavae
In Wilde's case, an adult, the right vena cava (called by him 'common iliac') joined near the liver with the left which passed over the aorta. Each of the cavae received four lumbar veins, aiid a spermatic vein. The right received one and the left two renal veins; the left vena cava received the left suprarenal and the unpaired stem the right suprarenal. At the level of the 5th lumbar vertebra the two cavae are joined together by an anastomosis running behind the aorta obliquely from the left upwards to the right.
Nicolai found in a 74-year-old woman the right inferior vena cava 1.4 cm. broad formed by the junction of the right common iliac vein with a branch from the left of ramus communicans (called by him the 'left common iliac'). From its formation at the level of the bifurcation of the aorta the right cava ran at the right of the aorta a distance of 9 cm. to the level of the hilus of the kidney where it was joined by the left inferior vena cava. The two cavae here formed a common stem 2 cm. broad. At the point where the internal and external iliac veins
DUPLICATION OF INFERIOR VENA CAVA 481
join, tlicy divide into the ramus coninninicans and left inferior vena cava. This latter ran vertically for 11 cm. to the height of the hilus of the kidney where after a horizontal course of 5.5 cm. it joined the rijjiit vena cava. There were two right renal veins, both entering the right vena cava opposite the junction of the left. The superior of these received the vena azygos. On the right a spermatic vein could not be seen and but two small veins that could be called lumbar veins. The common stem received only the right suprarenal vein which is very short. In its inferior part the left vena cava received the left spermatic vein. Where the left vena cava bent to join the right it received the left renal vein. The horizontal portion of the left vena cava received a large vein which was formed by a short suprarenal and the vena hemiazygos.
In Lobstein's case the common vena cava at the accustomed entering place of tlie renal veins received the right and left venae cavae. The common stem received the right renal, right suprarenal, and a small stem that helped to form the vena azygos. The right vena cava received the right spermatic vein. The left vena cava received the left suprarenal, renal, and spermatic veins. No mention is made of lumbar A'eins. A strong anastomosis occurred between the venae cavae running from the place of union of left external and internal iliac veins (which union lies somewhat deeper than the right), obliquely superiorly to join the right- vena cava. The middle sacral vein came off from this anastomosing branch.
Lagneau found in a young man that the left primitive iUac vein ascended parallel to the aorta to form the left inferior vena cava which joined the right, at the level of the kidneys. In its superior part it received: the left testicular vein, a large trunk resulting from the union of two large left emulgent veins, and a capsular vein of the same side. The right external and internal ihac veins formed the 'primitive iliac vein,' the ascending vein of the right side. Similarly, the left external and internal iliac veins communicating through a vast anastoy mosis formed the 'primitive ihac' and as such arose as the left inferior vena cava. The left external iliac vein received behind the primitive iliac artery a considerable trunk resulting from the union of the two internal ihac veins.
Besides the two inferior venae cavae, one can observe on this subject first, that the two internal ihac veins and the left external ihac vein joined in order to form the trunk of the left inferior vena cava, while the right inferior vena cava received only the right external iliac. Sec THE ANATOMICAL RECORD, VOL. 6, NO. 12
482 MAUEICE H. GIVENS
ond, that on each side an anastomosis existed between the external and internal iliac veins.
Le Gendre found in a foetus with enlarged pelvis of kidney the common iliac veins continued superiorly as two venae cavae. The left vena cava crossed the aorta obliquely to join the right at the level of the upper pole of the kidney. The right vena cava received the right renal vein while the left vena cava received two renal veins superior to the level of the ramus communicans. At the level of the hilus of the kidney the ramus communicans passed behind the aorta to connect the two cavae. No further description of the venous system is given.
Gruber describes a case in a man in which the common iliac vein ascended on both sides of the aorta as a double vena cava to join at the level of the first lumbar vertebra. The aorta 4 cm. wide running obliquely inferiorly for 12 cm. was surrounded by a 'verschobenen parallelagrammatischen' ring formed by the common iliac veins and their anastomoses. The right vena cava and its stems ran normally, only the vein was a httle farther laterally from the aorta than usual. The left common iliac vein lay at first behind the left internal iliac artery and the lower part of the left common iliac artery bent behind these, and ascended on the left of the aorta to the second lumbar vertebra and then crossed obliquely over the aorta at the lower border of the mouth of the superior mesenteric artery to join the right vena cava at the level of the first lumbar vertebra. There was a ramus communicans running from the left obliquely superiorly behind both stems of the aorta to join the right vena cava at the level of the 4th lumbar vertebra. The vena sacralis media was received by the ramus communicans. The right vena cava received the right renal, spermatic and four lumbar veins. The left vena cava received the left suprarenal, left renal, spermatic, and four lumbar veins. The azygos and hemiazygos veins were normal.
. Le Gendre describes in another man a case somewhat similar. The common iliac veins ran up on both sides of the aorta to join in front of the intervertebral fibro-cartilage between the last thoracic and first lumbar vertebra. Both cavae, being of about the same calibre, were connected by a ramus communicans which comes off partly from the left vena cava and partly from the left internal iliac vein and joins the right vena cava about 1 cm. above the junction of external and internal iliac veins. The ramus communicans received the vena sacralis media
DUPLICATION OF INFERIOR VENA CAVA 483
in its riglit half. The left vena cava ascended vertically to the upper border of the second lumbar vertebra and then crossed obliquely to join the right. The unpaired vena cava thus formed received the right suprarenal vein. The right renal, right luml)ar, and the right spermatic vein emi)tied into the right vena cava especially low. The left vena cava received the left suprarenal, renal, spermatic, and four lumbar veins. The vena azygos and hemiazygos are normal.
Walter described a case in a man in which the two venae cavae joined at the hilus of the kidney to form a short common vena cava inferior. The right vena cava ran vertically on the right of the aorta and received the two right renal, the right spermatic, and the four right lumbar veins. The left vena cava ran vertically on the left of the aorta and received the left suprarenal, renal, spermatic, and lumbar veins. A ramus communicans of about the same calibre as the vena cava running obliquely supcriorlj- from right to left connected the two at the level of the 5th lumbar vertebra.
Walter described a second case in a woman in which two large venous stems joined at the level of the 1st lumbar vertebra to form a common inferior vena cava. The left stem ascended vertically to the point where it crossed the aorta obliquely to join the right vena cava which ascended on the right of the aorta. On each side the venae cavae arose in their normal place from the internal and external ihac veins. The right iliac vein lay normally while the left ran lateral to its artery. From the right common and partlj' from the internal iliac veins at the junction of internal and external iliacs the reasonably large ramus communicans arose. It ran across the vertebral column between the 4th and 5th lumbar vertebrae obliquely upward to join the left common iliac. In front of the second sacral vertebra there was a short anastomosis between the internal ihacs. At the level of the 4th lumbar vertebra there was a small ramus communicans running behind the aorta to connect the two venae cavae. The unpaired vena cava received the right renal vein. No mention is made of any further tributaries of the venae cavae.
In the foregoing cases the two cavae joined one another between the limits of the 12th thoracic and the 2d lumbar vertebra. In those cases having a ramus communicans the two cavae joined between the 1st and 2d lumbar vertebra while in the others the point of junction was of more variable extent. The cavae are of variable lengths, but in the majority of cases the left was longer than the right as we would naturallj'
484 MAURICE H. GIVENS
expect. Sometimes the ramus communicans ran behind the aorta but usually in front of it. The superior connection of the two cavae corresponding to the left renal vein did not pass behind the aorta in any case.
The inferior vena cava is now considered to be a compound vessel consisting of a part of the heart, part of the vena hepatica communis, dilated sinusoids of the liver, part of the right subcardinal vein, and a section of the right posterior cardinal vein.
As has been shown by various investigators, more recently by Lewis in the rabbit embryo, the iliac veins empty into the post cardinal vein on each side. Running parallel anteriorly with each of these posterior cardinal veins there is later developed another vein, the subcardinal. These veins have numerous anastomoses with the posterior cardinal and with one another. At the level of the future left common iliac, a strong anastomosis develops between the two posterior cardinals. A second strong anastomosis develops at the level of the future renal veins. This connects the posterior cardinal and subcardinal veins on the two sides. Both of these anastomoses persist and later become more strongly developed. On the left side the posterior cardinal and subcardinal between these crossed anastomoses normally disappear. The most inferior crossed anastomosis enlarges and becomes the left common iliac vein. The superior transverse anastomosis persists and enlarges to form the right connection between the persistent posterior and subcardinal veins. The connection with the right posterior cardinal superior to this point is lost and the right subcardinal inferior to the connecting branches disappears or becomes very small. On the left side the anastomosing branch also enlarges and becomes the renal.
If the above interpretation of the developmental changes is correct, we have in the first specimen described by me a persistence, instead of a disappearance, of the left posterior cardinal and possibly also in the neighborhood of the renal, of the subcardinal. The blood instead of all passing through the left common iliac, as is normal, divides and part passes through the persistent posterior and subcardinal veins as far as the superior crossed anastomosis where joining with the blood from the renal
DUPLICATION OF INFERIOR VENA CAVA 485
jimi sii])raronal it crosses in the i)orsistont superior crossed iiiiastomosis to empty into the riglit vena cava. In the second specimen in place of the left posterior cardinal remaining: persistent as far as the superior crossed anastomosis (renal) one of the mnnerous secondary anastomoses which connect the posterior and subcardinal inferior to this level has become enlarged and remains as the permanent connection between the right and left sides. In addition to this the inferior transverse anastomosis which usually becomes the left common iliac vein has become very much reduced and persists only as a very small connecting vein. This specimen shows a persistence of several loops so frequently seen in developing veins but as a rule disappearing in this vein.
The majority of the cases described in the literature correspond very closely with the first case of mine. In those specimens described by others in which there was no inferior connection between the two sides, the crossed anastomosis which normally develops into the left common iliac vein either completely disappears or did not develop at all.
I wish to thank Professor Kerr for his valuable suggestions and criticisms.
BIBLIOGRAPHY
Broca, M. 1852 Duplicite de la veine cave; deux exemples. Bulletins de la Societe Anatomique, 27, p. 474.
Flesch, M. 1876 Scheinbare Verdoppelung der Vena Cava Inf. Verhandungen der Physikal-]\Iedicine Gesellschaft in Wuzlung. Bd. 10, p. 44.
Gruber, W. 1880 Virchow's Archiv, Bd. 81, p. 465. 1881 Virchow's Archiv, Bd. 86, p. 493.
KoLLMAX, J. 1893 Abnormitaten im Bereich der Vena Cava Inf. Anatomischer Anzeiger, Bd. 8.
LoBSTEix, J. T. 1760 Inaugural dissertation: De nervo spinali ad par vagum accesoris. August.
Lagneau 1863 Veine cave inferieure double chez un jeune homme. Bulletins de la Societe Anatomique, vol. 78, p. 344.
Le Gendre Quoted from Xicolai.
Lewis, F. T. 1901-02 The development of the vena cava inferior. Am. Jour. Anat., vol. 1, p. 229.
486 MAURICE H, GIVENS
NicoLAi, N. 1886 Zwei Falle von Partieller Verdoppelung der Vena Cava Inf. 8°. Kiel.
Walter, J. 1884 Inaugural dissertation; Ueber die partielle Verdoppelung der Vene Cava Inf. Erlangen. 4°. Stuttgart.
Wilde, J. C. 1740 Observationes anatomicae rariores. Comment. Acad. Sc. Imp. Petropal. Tome 12, Taf. 8, fig. 1, p. 312.
Zaaijer, T. 1872 Anomalie dans la composition de la veine cave inferieure. Arch. Mere d. Sc. Exactes. La Haj^e, Tome 7, p. 451-453.
Tin-: HKLATION Ol' THE SINO-AURICULAR NODE TO THE VENOUS VALVES IN THE HUMAN HEART
ADKLi' ()IM'i:mii;imi:ii and b. s. oppenhki.mi;i{
From the I'dtliologicul Lahordlory of Columbia University
ONE riGURK
The reason for publishing this finding in the human heart is to present evidence that the sino-auricular node hes within the region which corresponds to the sinus venosus of the cold-blooded vertebrates. The sino-aui'icular node is now believed by many to be the site of origin of the heart l^eat in mammals/ just as the sinus venosus is known to be the primum movens in the coldblooded vertebrates. In the lower vertebrate heart, the sinus venosus is a distinct chamber separated from the auricular canal by the venous valves, so that the free margin of the valves forms the boundary hne between the cavity of the sinus and that of the auricular canal. But as in the adult human heart the venous valves in this region have been greatly modified and shifted in position, it has not been definitely shown on which side of the valve the sino-auricular node is located.
In the hearts of the two foetuses and the one child's heart about to be described we found the venous valve present and the sinoauricular node (that is the pacemaker of the heart) to the sinus side of the valve. The hearts, which were secured through the courtesy of Dr. E. A. Park and Dr. B. Rosenbluth, were from an infant three weeks old which had died of pneumonia and from two foetuses 16 cm. and 21 cm. long, respectively.
Upon gross examination the infant's heart was found to l^e normal. The heart was fixed in alkalinized formalin. For microscopic exami 1 See the work of Wybauw, Lewis and Oppenheimer, Cohn and Kessel, Brandenburg and Hoffmann, Ganter and Zahn, and the opinions of W. Koch and of Hering.
487
488 ADELE OPPENHEIMER AND B. S. OPPENHEIMER
nation the region of the sino-auricular node was excised. This lilock consisted of the wall of the right auricle on either side of the sulcus terminalis of His; extending dorsad as far as, and including a portion of the endocardium of the left auricle and a part of the superior and inferior venae cavae, extending ventrad beyond the crista terminaiis of His so as to include a strip of pectinate muscles all along the length of the crista. Moreover this block extended along both sides of the crest of the right auricle, thus including not only the part already described on the lateral aspect 'of the auricle on either side of the sulcus, but also the auricular wall on the median aspect facing the aorta. On the lateral aspect the area reached almost to the auriculo-ventricular groove; on the median face it extended from the crest down to the level of the origin of the aorta. This piece was embedded in celloidin-paraffin, cut into sections 15 mi era thick, and stained wdth Weigert's iron-haematoxylin and van Gieson's picric-acid fuchsin solution. The sections ^vere horizontal, that is perpendicular to the length of the crista terminaiis of His and to the epi- and endocardium.
On microscopic examination the typical nodal tissue was found in the usual position, namely, at the junction of the superior vena cava with the right auricle and along the crista terminaiis under the sulcus of His. The node could be identified even under low magnification by its wealth of connective tissue, crowded nuclei, and the dense syncytial character of its musculature; moreover by its relationship to its nutrient artery.
At the junction of the node and crista a valvular cusp was found, as well as its companion cusp on the opposite side of the endocardium. These cusps consist of a central core of connective tissue with a few muscular elements, covered with i, single layer of flattened endocardial cells. The crista and the pectinate muscles were situated anterior to the valves; the musculature of the superior vena cava, atrium and sino-auricular node posterior to the valves ; the endocardium covering the auricular wall in front of the valves is thinner than that covering the auricular wall posterior to them.
In Keith and Flack's classic papers,- the i)Osition of the venous valve in the human heart was suggested in the exact situation in which we have actually found it in the heart here described. Keith and Flack identified the remnant of the sino-auricular junction in the human heart by comparing it with the turtle's
- Keith and Flack, Jour, of Aiiat. and riiysioL, 1907, vol. 41, p. 172.
NODE AM) \ AIAKS I.\ TIIK IHMAX IIKAKT
489
Fig. 1 Showing horizontal section of the right auricle in the region of the sinoauricular node of an infant's heart. Photomicrograph X 16. 1-1, venous valve; 2, ordinary cardiac musculature; 3, musculature of the sino-auricular node; 4, taenia or crista terminalis of His, which, lined with thin endocardium, lies on the auricular side of the valve. The elongated cavitj-, lined with thick endocardium, is situated on the sinus side of the v^alve.
490 ADELE OPPENHEIMER AND B. S. OPPENHEIMER
heart in which there is a venous valve. The} showed (fig. 6 of their paper) that in the turtle's heart the endocardial covering of the auricular musculature is thinner than that of the sinus, and that the venous valve is situated at the junction of the two varieties of endocardium. In the human heart here described and in the heart of the two foetuses examined, the sino-auricular junction as such is almost as clearly shown as in the more primitive hearts, for the venous valve is actually present lying between the musculature (auricular) covered by a thin endocardium and that (sinus) lined with a thick endocardium. The nodal tissue was found at the base of the venous valve in the region covered by thick endocardium. The relations in the foetuses' hearts were found to be the same as those in the infant's.
In brief, in the infant and foetus' hearts here presented the sino-auricular node lay in close proximity to the base of the venous valve, in what corresponds to the sinus venosus of cold-blooded vertebrates.
AN ACKNOWLEDGMENT OF FEDOROWS WORK ON THE PULMONARY ARTERIES
JOHN LEWIS BREMER
From the Harvard Medical School, Boston
Li a recent paper^ I described the development of the puhnonary arteries in rabbit embryos, and showed that, contrary to the heretofore accepted views, originated by Rathke and His, these vessels are not branches of the last or pulmonary aortic arches, but caudal prolongations of the ventral aortae. These ventral aortae are represented by a network of capillary vessels which grows caudally from the truncus arteriosus, between the ventral wall of the pharynx and the dorsal wall of the pericardial cavity, extending from side to side across the median hne, giving off, between the gill pouches, lateral sprouts which join others from the dorsal aortae to form the second, third and fourth aortic arches. To quote from the paper cited:
A further extension of the plexus of the ventral aorta, situated between the floor of the pharynx and the dorsal wall of the pericardial cavity, but prevented from crossing the median line by the presence of the median, pharyngeal outgrowth to form the trachea, reaches to the lungs as the pulmonary arteries, which are later joined by vessels springing from the dorsal aortae. These vessels, which may be double and plexi form, constitute the fifth (and sixth) arches The sprouts
for this last arch arise chiefly from the dorsal vessels, instead of from the ventral net. I also wish to point out that the net grows beyond the arch, before the arch has become complete. In other words this extension of the ventral aortic net forms well defined pulmonary arteries, one on each side, before the pulmonary arch exists; the pulmonary artery is in no sense a branch of the pulmonary arch, and moreover, in the strictest sense, the arch extends only from the dorsal aorta to the pulmonary artery, the ventral part of the vessel usually called the arch is really the ventral aorta. The persistent pulmonary arteries are entirely ventral; they have been joined during embryonic life by branches from the dorsal aorta, but such branches are only temporary.
On receipt of a reprint of this paper, Dr. V. Fedorow, of the Military Medical Academy, St. Petersburg, Russia, sent me a
1 Am. Jour. Anat., vol. 13, no. 2, 1912.
491
492 JOHN LEWIS BREMER
copy of a short article^ published by him in Russian, in which he shows that in the guinea pig the puhnonary arteries arise in the same manner as I have described for the rabbit. Fedorow's work appeared before mine, and I wish to take this opportunity of ascribing to him the priority, and also of bringing to the notice of American anatomists a paper which might well remain unknown because of the language in which it is printed. With this in view I offer the following passages from this article:
The pulmonary arteries of the guinea pig in the earlj^ stages are extremeh' delicate and can be traced in their surrounding thick mesenchyma only with great difficulty.
In the embryo of the eighteenth day, with 30 somites, the first two pairs of aortic arches are obliterated, the third and fourth pairs are fullj' formed. From the medial wall of the last arches the aa. pulmonales issue on each side. They begin near the truncus arteriosus ventral to the middle part of the pharynx, which is quite large at this point. The arteries run caudally on the ventral surface of the oesophagus, dorsal to the pericardial cavity, and quite near to each other. Further down, the oesophagus appears compressed laterally, and the arteries lie lateral to its ventral part, which projects in the form of a pointed keel. The pulmonary arteries end blindly, traversing about 20 segments (240 m.).
In another embryo of the same age, with 29 somites, the arteries extend further, their diameter varying at different points, and it may be anastomose with the vessels of the oesophagus. Similar anastomoses frequently occur later. One notices the double origin of both arteries from their corresponding arches, and they may even join one another near the arch. Island formation occurs along the course of the arteries.
In the embryo of the nineteenth day, with 32 somites, the third and fourth pairs of aortic arches are present, the sixth pair represented by blind growths both from the dorsal aortae and from the truncus arteriosus. The delicate pulmonary arteries begin from the sixth pair as short growths. Properly, they are the elongated aa. pulmonales of the earlier stages. They run caudally ventro-lateral to the oesophagus, and anastomose with its vessels.
It will be seen that the two articles run closely parallel to each other; that, though Fedorow speaks of the pulmonary arteries as arising from the fourth arch, while I prefer to call them extensions of the ventral aorta, both agree that they are not originally sprouts from the sixth or pulmonary arches, as has so
2 Communications of the Militar\' Med. Acad., St. Petersburg. Russia, vol. 22, no. 1, 1911.
FEDOHow's WOHK ON THK Pl'LMONARY ARTERIES 41)3
louj; been held true. In two spocios, rabbit and guinea pig, tliis lias now been worked out. This is the more interesting to me IxH'ause of the fact that in the furtluM- development of these arteries these same two species differ markedly, as pointed out in previous communications. ^ In the rabbit and many other species, including man, the puhnonary aorta becomes the permanent arteria pulmonalis communis, from which the right and left arteries branch, while in the pig and the guinea pig, by an anastomosis of the two puhnonary arteries and the obUteration of one side of the loop thus made (by the proximal portions of the two sixth arches and the proximal portions of the two pulmonary arteries), the permanent arteria pulmonalis communis is much longer, and comprises, besides the pulmonary aorta, the proximal, or ventral, part of the sixth arch (which is really ventral aorta), the upper part of the pulmonary artery of one side, and the anastomosis.
In the pig the left side of the loop remains permanently in communication with the two pulmonary arteries; in the guinea pig the left side becomes obhterated the right side remains in the adult. In this connection it is of interest that-Fedorow, while confirming the facts just referred to, reports in this same paper one case, in a guinea pig embryo of twenty-four days, in which the left side of the loop, instead of the right, remained as a permanent vessel; in other words, in which the guinea pig embrj^o simulated the pig. This, it seems to me, must be an anomaly, and one that I am unable to explain; any more than I can explain why these two species should differ in this respect as they normally do.
' Am. Jour. Anat., vol. 1, no. 2, 1902. Anat. Rec, vol. 3, no. 6, 1909.
BOOKS RECEIVED
THE TERATOLOGY OF FISHES, James F. Gemmill, lecturer in embryology, Glasgow University, and in zoology, Glasgow Provincial Training College, 25 plates, 73 pages including index, 1912. James Maclehose and Sons, Glasgow.
