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Baxter JS. Aids to Embryology. (1948) 4th Edition, Bailliere, Tindall And Cox, London.

Historic Disclaimer - information about historic embryology pages
Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding. (More? Embryology History \| Historic Embryology Papers)

Chapter XIV The Transmission of Hereditary Characters

Every potential individual, that is, every fertilised ovum, commences development with a complement of hereditary factors (genes) derived from both parents at the time of union of the germ cells in fertilisation. These inherited factors operate during development, both before and after birth, to produce an individual resembling the parents. The environment, both prenatal and post-natal, may influence some of these hereditary characters and modify them, but there are certain characters which cannot be affected by the environment and hence are said to be determined at fertilisation. Examples of these are the blood group to which the person belongs and the colour of the eyes. The study of these hereditary factors, and the laws which govern their transmission from parents to offspring, is known as the science of genetics.

Genetic laws are fundamentally the same for plants and animals, and since many generations of plants and lower animals can be investigated in a relatively short period of time, the study of genetics has largely been based on them. In addition, certain forms possess chromosomes particularly favourable to the genetic analysis of experimental procedures. But in all cases where genetic laws have been tested in lower forms they have been found applicable to human hereditary.

Parent ^ Tfc\l (T) "H Dw&rf (d)

fj. AU hybrid Tidls (Td)

1 ^ l

Td

Hybrid Tidls

dd

Pure Dvj&rfs

1 1 1 r

Td Td dd TT

1

i

d Td dd

k dd All Pure Ow^ris

Fig. 42 . - Schematic Table showing Mendelian Inheritance AS APPLIED TO TALL AND DWARF PEAS.

T = tall ; d = dwarf.

The fundamental genetic laws are based on the experiments of Mendel (1866) on garden peas. Mendel studied the inheritance of a number of characters of this form, of which tallness and dwarfness may be taken as a typical example. If a tall pea and a dwarf pea were cross-fertilised and the resultant peas planted, all of the plants that grew from them were tall. These he called the first filial generation (Fj). These tall cross-bred plants were allowed to produce peas by self-fertilisation, and when such were sown the second filial generation (F a ) showed some plants that were tall and some that were dwarf, in the proportion of three tall to one dwarf. Peas derived from self-fertilisation of each of the dwarf plants were then sown, and they produced dwarf plants only ; seed from some of the self -fertilised tall plants produced both tall and dwarf offspring, in the proportion of three tall to one dwarf ; the remainder of the seed from the tall plants produced nothing but tall offspring in the third (F s ) generation (see Fig. 42 for details).

From these experiments it is clear that an attempt was being made by nature to separate the original pure characters of tallness and dwarfness in the parent stock from the hybrids. This is known as the law of segregation. The character of tallness, which was found in the F x generation, is known as a dominant character since it overshadows the recessive character of dwarfness. These characters are known to be caused by certain elements on the maternal and paternal chromosomes called genes.

Parents

â€” Y

+ dd

4

P&rent G&mefes

T

Â»

d

j 1

F 1

.Td

Fj. Q&metes

_T.

d. T. d.

F t T ~ v7~ 1 ' >

F * TT. Td. Td. dd.

Fig. 43. â€” Schematic Table to show Segregation of the Tall and Dwarf Genes in the Gametes of Peas.

T = tall ; d = dwarf.

Consideration of Fig. 43 will indicate how these dominant and recessive factors become separated out during breeding. The parent stock possessed either the character of tallness or dwarfness in pure form, that is, when self -fertilised they always bred true. The first filial generation (Fj) were all tall since the gene for dwarfness was present but masked by the dominant tall (T) gene. The gametes (sex cells) of the Fj generation contained the genes for tallness and dwarfness in equal numbers so that when such plants were self-fertilised the dominant T gene would be present in three out of four of the offspring and they would all be tall plants. In one out of the four, two d (dwarfness) genes would be present and hence these plants would be dwarfs, and on further selffertilisation would continue to breed truly dwarf. One of the three tall plants would contain only genes for tallness and so on self-fertilisation it would continue to breed true for the character of tallness. The remaining two tall plants contained Td genes, and further inbreeding of them would result in the formation of dominant and recessive forms in the ratio of three dominant to one recessive.

In human genetics there are certain clear-cut cases of inheritance due to dominant factors. Examples of these are congenital brachydactyly, syndactyly, and congenital night blindness. Also black hair colour is dominant over brown hair colour, and so is brown iris colour over blue.

Mendelian laws have been applied to animals and they have been found to hold equally good for them. For example, the colour of the ordinary brownishgrey wild mouse is due to bands of pigment in its hair ; black at the base and yellow at the tip. This is known as â€œ agouti â€ colouration. But in fancy mice there is a variety in which the hair appears black, due to the absence of the yellow tip to the hair. If a pure agouti mouse is crossed with a black or non-agouti, the offspring at Fj are all agouti in colour â€” that is, the agouti factor is dominant over the non-agouti, which is the recessive factor. If however these hybrids are inbred, the F 2 generation comes out as 25 per cent, pure agouti, 50 per cent. hybrid agouti, and 25 per cent, pure non-agouti. This shows the Mendelian ratio of 1 : 2 : 1.

In both the agouti (A) and the non-agouti (b) mice there is a variety with straight hair (S) and a variety with wavy hair (w). If a non-agouti wavy mouse (bw) be crossed with an agouti straight mouse (AS), the F! animals will be agouti straight (AbSw) since A is dominant over b, and S over w. Then if these F x hybrids are inbred the genes will be segregated out as follows :

Agouti straight (AS) Agouti wavy (Aw) Non-agouti straight (bS) Non-agouti wavy (bw) .

9

3

1

In these experiments two new types have been produced â€” the agouti wavy and the non-agouti straight. The combinations of dominant and recessive characters which have produced these adult forms are shown in Fig. 44. It will be seen that the AbSw hybrids gave rise to four gametes in equal numbers :

AS : Aw : bS : bw.

These combinations take place in the ova as well as in the spermatozoa and since every kind of ovum is likely to be fertilised by any kind of spermatozoon, there are 4 s = 16 possible combinations yielding 9 agouti straight, 3 non-agouti straight, 3 agouti wavy and 1 non-agouti wavy. The several genes of the cross are being segregated out as is shown in Fig. 44. This rule holds good for other possible combinations.

The blood groups A, B, AB and O are transmitted from parents to offspring in accordance with Mendelian laws. The principles involved may be briefly stated as follows :

When red blood corpuscles of one animal species are mixed with the serum of another species they become clumped together or agglutinated. There is in the serum a substance (an agglutinin) which attaches itself to an agglutinable substance (agglutinogen) in the red cells and clumping occurs. In man, blood cannot be transfused from one person to another unless the two bloods are compatible. The important factor is the agglutinogen in the red cells of the donor ; if that is incompatible with the agglutinin in the recipientâ€™s serum, serious consequences will result in transfusion. From the standpoint of heredity the A and the B agglutinogen factors are dominant over the O factor. If a childâ€™s blood belongs to either group A or B one or other of its parents must have blood belonging to such a group.

AS

Aw

bS

bw

Sperms

" J t

A5

A A 55

Pure Agouti.

^ure

Straight.

AASw Pure Agouti. Hybrid Straight.

AbS5

Hybrid Agouti.

Pure

Straight.

AbSw Hybrid Agouti, | Hybrid

Straight. I

Aw

A A5w

Pure Agouti. Hybrid

Straight.

AAww

Pure Agouti. Pure Wave.

AbSw

Hybrid Agouti. Hybrid Straight.

Abww 1 Hybrid j

Agouti.

Pure Wave. #

bS

AbSS

Hybrid Agouti .

Pure

Straight.

AbSw

4

Hybrid

Agouti.

Hybrid

Straight.

bbSS

Pure

Mon Agouti . Pure

Straight.

bbSw

Pure

Mon Agouti . Hybrid Str&igW t .

bw

Ab Sw

Hybrid Agouti . Hybrid Straight.

Abww

Hybrid Agout i .

Pure

Wave

bbSw

Pure

Non Agouti . Hybrid Straight.

bbw w

Pure

Non Agouti.

Pure

Wave.

Fig . 44. - Schematic Table to show the possible Combinations of the genes for straight hair, wavy hair, Agouti Colour and Non-Agouti Colour in Mice. A = agouti ; S = straight ; b = non-agouti ; w - wavy.

Genes do not always act in the relatively simple manner just described. There may be incomplete

Parents

XhY

[H&emopluVic

Daughter free from disease but CAN TRANSMIT.

XbX?

Marries

Son free from Â® AY disease but CANNOT TRANSMIT, normd male.XY

XkY <?

T

XwX?

~~\ â€”

XX?

â€œ1

XY o* *

fUemophi'ic Son. Daughter free Normal Daughter. Normal Son.

from disease but CA N

TRANSMIT.

Fig. 45. â€” Schematic Table to show the Transmission of haemophiliac genes through three generations.

X, female chromosome with non-haemophiliac gene ; Xh, female chromosome with haemophiliac gene ; Y, normal male chromosome.

action of a gene or there may be a lethal gene present. An example of the latter is the disease in man called Huntingdonâ€™s chorea. Here the disease appears first about 35 years of age and the patient rarely lives longer than ten to twelve years after that time. The carrier is eventually killed by his or her predisposition to the disease but only after he or she has passed on the lethal gene to the offspring.

Sex-linked characters are important in certain rare diseases such as haemophilia. The factor here is transmitted on an X chromosome. If a haemophiliac male marries a normal unrelated female all their daughters must necessarily receive one haemophiliac X chromosome from the father and a normal X chromosome from the mother. The sons all receive a normal Y chromosome from the father and a normal X chromosome from the mother. They therefore do not suffer from the disease, nor can they transmit it to their offspring. But the daughters all have a haemophilac X chromosome, and they will necessarily transmit the disease to 50 per cent, of their sons after marriage with a normal male.

Appendix

Ossification Times

The ossification periods have been widely studied, but the work of Hess (i9 2 3)> although differing in some respects from that usually given in textbooks on osteology, is now recognized as being the most accurate series of observations at present available. These observations may be summarized as follows :

7th week : Mandible, diaphysis of clavicle.

8th week : Diaphysis of humerus, radius, and ulna. 9th week : The terminal phalanges, the 2nd and 3rd basal phalanges, and the 2nd and 3rd metacarpal bones of the hand ; the ilium ; the 2nd and 3rd metatarsals, and the terminal phalanges of the foot bones.

10th week : 1st rib, and the 4th and 1st basal phalanges of the hand.

10th to 12th week : 4th, 5th, and 1st metatarsals.

11th to 1 2th week : The basal phalanx of the 5th digit, and the middle phalanges of the 2nd, 3rd, and 4th digits of the hand.

13th to 14th week : All the remaining metatarsals and the phalanges of the foot except the last phalanx of the 5th digit.

13th to 1 6th week : The middle phalanx of the 5th finger.

1 6th to 17th week : Descending ramus of ischium.

17th to 20th week : Odontoid process of axis.

2 1st to 24th week : Sternum.

2 1st to 28th week : Descending ramus of pubis.

2 1st to 29th week : Calcaneus (os calcis).

24th to 32nd week : Talus (astragalus).

33rd to 36th week : Last phalanx of the 5th digit of foot.

35th to 48th week : Distal epiphysis of femur, and occasionally the proximal epiphysis of tibia.

The wide variation in these figures might be accounted for by the statement of Pryor (1927), that ossification begins at an earlier date in female foetuses than in the male.

Historic Disclaimer - information about historic embryology pages
Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding. (More? Embryology History \| Historic Embryology Papers)

Cite this page: Hill, M.A. (2024, June 18) Embryology Book - Aids to Embryology (1948) 14. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Aids_to_Embryology_(1948)_14

What Links Here?

@@ Line 1: / Line 1: @@
 {{Baxter1948 header}}
-==Chapter XIV  The Transmission Of Hereditary Characters==
+=Chapter XIV  The Transmission of Hereditary Characters=
-Every potential individual, that is, every fertilised
+Every potential individual, that is, every fertilised ovum, commences development with a complement of hereditary factors (genes) derived from both parents at the time of union of the germ cells in fertilisation. These inherited factors operate during development, both before and after birth, to produce an individual resembling the parents. The environment, both prenatal and post-natal, may influence some of these hereditary characters and modify them, but there are certain characters which cannot be affected by the environment and hence are said to be determined at fertilisation. Examples of these are the blood group to which the person belongs and the colour of the eyes. The study of these hereditary factors, and the laws which govern their transmission from parents to offspring, is known as the science of genetics.
-ovum, commences development with a complement
-of hereditary factors (genes) derived from both parents
-at the time of union of the germ cells in fertilisation.
-These inherited factors operate during development,
-both before and after birth, to produce an individual
-resembling the parents. The environment, both prenatal and post-natal, may influence some of these
-hereditary characters and modify them, but there are
-certain characters which cannot be affected by the
-environment and hence are said to be determined
-at fertilisation. Examples of these are the blood
-group to which the person belongs and the colour of
-the eyes. The study of these hereditary factors, and
-the laws which govern their transmission from parents
-to offspring, is known as the science of genetics.
-HEREDITARY CHARACTERS 169
+Genetic laws are fundamentally the same for plants and animals, and since many generations of plants and lower animals can be investigated in a relatively short period of time, the study of genetics has largely been based on them. In addition, certain forms possess chromosomes particularly favourable to the genetic analysis of experimental procedures. But in all cases where genetic laws have been tested in lower forms they have been found applicable to human hereditary.
-Genetic laws are fundamentally the same for plants
+Parent ^ Tfc\l (T) "H Dw&rf (d)
-and animals, and since many generations of plants and
-lower animals can be investigated in a relatively
-short period of time, the study of genetics has largely
-been based on them. In addition, certain forms
-possess chromosomes particularly favourable to the
-genetic analysis of experimental procedures. But
-in all cases where genetic laws have been tested in
-lower forms they have been found applicable to
-human hereditary.
+fj. AU hybrid Tidls (Td)
-Parent ^ Tfc\l (T) "H Dw&rf (d)
-fj. AU hybrid Tidls (Td)
 ^ l
 Td
-Td
-Hybrid Tidls
-dd
-Pure Dvj&rfs
-1 1 r
-Td Td dd TT
-i
-d Td dd
-k dd
-All Pure
-Ow^ris
-y IG< 42 . â€” Schematic Table showing Mendelian Inheritance AS APPLIED TO TALL AND DWARF PEAS.
-T = tall ; d = dwarf.
-The fundamental genetic laws are based on the
-experiments of Mendel (1866) on garden peas. Mendel
-studied the inheritance of a number of characters of
-this form, of which tallness and dwarfness may be
-taken as a typical example. If a tall pea and a
-dwarf pea were cross-fertilised and the resultant
-peas planted, all of the plants that grew from them
-were tall. These he called the first filial generation
-(Fj). These tall cross-bred plants were allowed to
-produce peas by self-fertilisation, and when such
-were sown the second filial generation (F a ) showed
-some plants that were tall and some that were dwarf,
-AIDS TO EMBRYOLOGY
-in the proportion of three tall to one dwarf. Peas
-derived from self-fertilisation of each of the dwarf
-plants were then sown, and they produced dwarf
-plants only ; seed from some of the self -fertilised
-tall plants produced both tall and dwarf offspring,
-in the proportion of three tall to one dwarf ; the
-remainder of the seed from the tall plants produced
-nothing but tall offspring in the third (F s ) generation
-(see Fig. 42 for details).
-From these experiments it is clear that an attempt
-was being made by nature to separate the original
-pure characters of tallness and dwarfness in the
-Parents
-â€” Y
-+ dd
-P&rent G&mefes
-T
-Â»
-d
-j 1
-F 1
-.Td
-Fj. Q&metes
-_T.
-d. T. d.
-F t T ~ v7~ 1 ' >
-F * TT. Td. Td. dd.
-Fig. 43. â€” Schematic Table to show Segregation of the
-Tall and Dwarf Genes in the Gametes of Peas.
-T = tall ; d = dwarf.
-parent stock from the hybrids. This is known as the
-law of segregation. The character of tallness, which
-was found in the F x generation, is known as a dominant
-character since it overshadows the recessive character
-of dwarfness. These characters are known to be
-caused by certain elements on the maternal and
-paternal chromosomes called genes.
-Consideration of Fig. 43 will indicate how these
-dominant and recessive factors become separated out
-during breeding. The parent stock possessed either
-the character of tallness or dwarfness in pure form,
-that is, when self -fertilised they always bred true.
-The first filial generation (Fj) were all tall since the
-HEREDITARY CHARACTERS 171
-gene for dwarfness was present but masked by the
-dominant tall (T) gene. The gametes (sex cells) of
-the Fj generation contained the genes for tallness and
-dwarfness in equal numbers so that when such
-plants were self-fertilised the dominant T gene would
-be present in three out of four of the offspring and
-they would all be tall plants. In one out of the four,
-two d (dwarfness) genes would be present and hence
-these plants would be dwarfs, and on further selffertilisation would continue to breed truly dwarf.
-One of the three tall plants would contain only
-genes for tallness and so on self-fertilisation it would
-continue to breed true for the character of tallness.
-The remaining two tall plants contained Td genes,
-and further inbreeding of them would result in the
-formation of dominant and recessive forms in the
-ratio of three dominant to one recessive.
-In human genetics there are certain clear-cut
-cases of inheritance due to dominant factors. Examples of these are congenital brachydactyly, syndactyly, and congenital night blindness. Also black
-hair colour is dominant over brown hair colour, and
-so is brown iris colour over blue.
-Mendelian laws have been applied to animals and
-they have been found to hold equally good for them.
-For example, the colour of the ordinary brownishgrey wild mouse is due to bands of pigment in its
-hair ; black at the base and yellow at the tip. This
-is known as â€œ agouti â€ colouration. But in fancy
-mice there is a variety in which the hair appears
-black, due to the absence of the yellow tip to the
-hair. If a pure agouti mouse is crossed with a black
-or non-agouti, the offspring at Fj are all agouti in
-colour â€” that is, the agouti factor is dominant over
-the non-agouti, which is the recessive factor. If
-however these hybrids are inbred, the F 2 generation
-comes out as 25 per cent, pure agouti, 50 per cent.
-AIDS TO EMBRYOLOGY
-hybrid agouti, and 25 per cent, pure non-agouti.
-This shows the Mendelian ratio of 1 : 2 : 1.
-In both the agouti (A) and the non-agouti (b) mice
-there is a variety with straight hair (S) and a variety
-with wavy hair (w). If a non-agouti wavy mouse
-(bw) be crossed with an agouti straight mouse (AS),
-the F! animals will be agouti straight (AbSw) since A
-is dominant over b, and S over w. Then if these F x
-hybrids are inbred the genes will be segregated out
-as follows :
-Agouti straight (AS)
-Agouti wavy (Aw)
-Non-agouti straight (bS)
-Non-agouti wavy (bw) .
-In these experiments two new types have been
-produced â€” the agouti wavy and the non-agouti
-straight. The combinations of dominant and recessive characters which have produced these adult
-forms are shown in Fig. 44. It will be seen that the
-AbSw hybrids gave rise to four gametes in equal
-numbers :
-AS : Aw : bS : bw.
-These combinations take place in the ova as well as
-in the spermatozoa and since every kind of ovum is
-likely to be fertilised by any kind of spermatozoon,
-there are 4 s = 16 possible combinations yielding 9
-agouti straight, 3 non-agouti straight, 3 agouti wavy
-and 1 non-agouti wavy. The several genes of the
-cross are being segregated out as is shown in Fig. 44.
-This rule holds good for other possible combinations.
-The blood groups A, B, AB and O are transmitted
-from parents to offspring in accordance with Mendelian laws. The principles involved may be briefly
-stated as follows :
-When red blood corpuscles of one animal species
-HEREDITARY CHARACTERS
-are mixed with the serum of another species they
-become clumped together or agglutinated. There is
-in the serum a substance (an agglutinin) which
-AS
-Aw
-bS
-bw
-Sperms
-" J t
-A5
-A A 55
-Pure Agouti.
-^ure
-Straight.
-AASw
-Pure Agouti.
-Hybrid
-Straight.
-AbS5
-Hybrid Agouti.
-Pure
-Straight.
-AbSw
-Hybrid Agouti, |
-Hybrid
-Straight. I
-Aw
-A A5w
-Pure Agouti.
-Hybrid
-Straight.
-AAww
-Pure Agouti.
-Pure Wave.
-AbSw
-Hybrid Agouti.
-Hybrid
-Straight.
-Abww 1
-Hybrid j
-Agouti.
-Pure Wave. #
-bS
-AbSS
-Hybrid
-Agouti .
-Pure
-Straight.
-AbSw
-Hybrid
-Agouti.
-Hybrid
-Straight.
-bbSS
-Pure
-Mon Agouti .
-Pure
-Straight.
-bbSw
-Pure
-Mon Agouti .
-Hybrid
-Str&igW t .
-bw
-Ab Sw
-Hybrid
-Agouti .
-Hybrid
-Straight.
-Abww
-Hybrid
-Agout i .
-Pure
-Wave
-bbSw
-Pure
-Non Agouti .
-Hybrid
-Straight.
-bbw w
-Pure
-Non Agouti.
-Pure
-Wave.
-F IG . 44. â€” Schematic Table to show the possible Com
-BINATIONS OF THE GENES FOR STRAIGHT HAIR, WAVY
-Hair, Agouti Colour and Non-Agouti Colour in Mice.
-A = agouti ; S = straight ; b = non-agouti ; w - wavy.
-attaches itself to an agglutinable substance (agglutinogen) in the red cells and clumping occurs.
-In man, blood cannot be transfused from one person
-to another unless the two bloods are compatible.
-The important factor is the agglutinogen in the red
-AIDS TO EMBRYOLOGY
-cells of the donor ; if that is incompatible with the
-agglutinin in the recipientâ€™s serum, serious consequences will result in transfusion. From the standpoint of heredity the A and the B agglutinogen
-factors are dominant over the O factor. If a childâ€™s
-blood belongs to either group A or B one or other of
-its parents must have blood belonging to such a
-group.
-Genes do not always act in the relatively simple
-manner just described. There may be incomplete
-Parents
-XhY
-[H&emopluVic
-Daughter free from
-disease but CAN
-TRANSMIT.
-XbX?
-Marries
-Son free from
-Â® AY disease but
-CANNOT TRANSMIT,
-normd male.XY
-XkY <?
-T
-XwX?
-~~\ â€”
-XX?
-â€œ1
-XY o* *
-fUemophi'ic Son. Daughter free Normal Daughter. Normal Son.
-from disease
-but CA N
-TRANSMIT.
-Fig. 45. â€” Schematic Table to show the Transmission of
-HAEMOPHILIAC GENES THROUGH THREE GENERATIONS.
-X, female chromosome with non-haemophiliac gene ; Xh, female
-chromosome with haemophiliac gene ; Y, normal male
-chromosome.
-*
-action of a gene or there may be a lethal gene present.
-An example of the latter is the disease in man called
-Huntingdonâ€™s chorea. Here the disease appears
-first about 35 years of age and the patient rarely
-lives longer than ten to twelve years after that time.
-The carrier is eventually killed by his or her predisposition to the disease but only after he or she
-has passed on the lethal gene to the offspring.
-Sex-linked characters are important in certain rare
-diseases such as haemophilia. The factor here is
-HEREDITARY CHARACTERS
-transmitted on an X chromosome. If a haemophiliac
-male marries a normal unrelated female all their
-daughters must necessarily receive one haemophiliac
-X chromosome from the father and a normal X
-chromosome from the mother. The sons all receive a normal Y chromosome from the father and
-a normal X chromosome from the mother. They
-therefore do not suffer from the disease, nor can
-they transmit it to their offspring. But the daughters
-all have a haemophilac X chromosome, and they will
-necessarily transmit the disease to 50 per cent, of
-their sons after marriage with a normal male.
-APPENDIX
-OSSIFICATION TIMES
-The ossification periods have been widely studied,
-but the work of Hess (i9 2 3)> although differing in
-some respects from that usually given in textbooks on
-osteology, is now recognized as being the most accurate series of observations at present available.
-These observations may be summarized as follows :
-th week : Mandible, diaphysis of clavicle.
-th week : Diaphysis of humerus, radius, and ulna.
-th week : The terminal phalanges, the 2nd and 3rd
-basal phalanges, and the 2nd and 3rd metacarpal
-bones of the hand ; the ilium ; the 2nd and 3rd
-metatarsals, and the terminal phalanges of the
-foot bones.
-th week : 1st rib, and the 4th and 1st basal phalanges of the hand.
-th to 12th week : 4th, 5th, and 1st metatarsals.
-AIDS TO EMBRYOLOGY
-nth to 1 2th week : The basal phalanx of the 5th
-digit, and the middle phalanges of the 2nd, 3rd,
-and 4th digits of the hand.
-th to 14th week : All the remaining metatarsals and
-the phalanges of the foot except the last phalanx
-of the 5th digit.
-th to 1 6th week : The middle phalanx of the 5th
-finger.
-6th to 17th week : Descending ramus of ischium.
-th to 20th week : Odontoid process of axis.
-1st to 24th week : Sternum.
-1st to 28th week : Descending ramus of pubis.
-1st to 29th week : Calcaneus (os calcis).
-th to 32nd week : Talus (astragalus).
-rd to 36th week : Last phalanx of the 5th digit of
-foot.
-th to 48th week : Distal epiphysis of femur, and
-occasionally the proximal epiphysis of tibia.
-The wide variation in these figures might be accounted for by the statement of Pryor (1927), that
-ossification begins at an earlier date in female foetuses
-than in the male.
-INDEX
-Accessory tubercle of pinna, 74
-Acoustico-facial complex, 71
-Acrocephaly, 167
-Acrosome, 3
-Adrenal gland, 61
-Alimentary canal, 75
-Allantois, 34, 141, 142
-Amnion, 15, 32
-Amnio tic cavity, 15, 16
-fluid, 33
-Amastia, 43
-Anencephaly, 59
-Angiogenesis, 34
-Aorta, branches of, 114
-coarctation of, 118
-Aortic arches, 109
-trunk, 105
-Appendicular skeleton, 166
-Appendix, 92
-Artery or arteries,
-axial, lower limb, 116
-femoral, 116
-intersegmental, 113
-pulmonary, 117
-radial, 115
-ulnar, 115
-of upper limb, 115
-anomalies of, 118
-development of, 116
-Atresia, of aorta, 108
-intestinal, 93
-of pulmonary artery, 108
-Atria, development of, 104
-Atrio-ventricular bundle, 106
-Auditory apparatus, development of, 73
-Auditory nerve, 71
-ossicles, 74
-Autonomic nervous system, 61
-Axial skeleton, 161
-Bicornuate uterus, 151
-Bipartite uterus, 151
-Bladder, development of, 143
-Blastocyst, 14
-Blood cells, 130
-Body stalk, 99
-Bone, histogensis of, 159
-Bony labyrinth, 72
-Bowmanâ€™s capsule, 140
-Brain, development of, 58
-Branchial arch arteries, 109
-Branchio-motor cells, 52
-Breast, anomalies of, 43
-Buccopharyngeal membrane,
-, 75
-Bulbus cordis, 100
-Caecum, 90, 92
-Canal of Schlemm, 66
-Cardiogenic area, 100
-Carotid body, 112
-sinus, 1 12
-Central nervous system,
-anomalies of, 59
-Cerebral aqueduct, 53
-commissures, 56
-cortex, 57
-Cervix, 148
-Chorion, 29, 99
-frondosum, 31
-laeve, 31
-Choroid, 66
-Chromaffin cells, 61
-Chromosomes, 9
-Circulation, at birth, 128
-foetal, 128
-Circulatory system, 99
-Cleft palate, 86
-sternum, 167
-Clitoris, hypertrophy of, 155
-Cloaca, 1 41
-persistent, 144
-Cloacal membrane, 75
-Club-foot, congenital, 167
-Coarctation of aorta, 118
-Cochlea, 71, 73
-Coelom, extra-embryonic, 19
-Coelomic cavities, 132
-Coloboma, congenital, 67
-Colon, 92
-Cornea, 66
-Corona radiata, 8
-Coronary sinus, 105
-77
-AIDS TO EMBRYOLOGY
-Corpus albicans, 21
-callosum, 57
-luteum, 20, 21
-striatum, 56
-Corti, organ of, 72
-Cotyledons, 31
-Crista acoustica, 71
-Cyclopia, 68
-Cystic kidney, congenital, 140
-Cuvier, duct of, 119
-Deafness, congenital, 74
-Decidua capsularis, 29, 31
-Deciduous teeth, 80
-Dental fibrils of Tomes, 81
-papilla, 80
-Dextrocardia, 108
-Diencephalon, 48, 53
-Dorsal aorta, branches of, 112
-Double heart, 108
-Ductus arteriosus, no
-persistence of, 118
-Ductus reuniens, 71
-Duodenal stenosis, 93
-Duodenum, 91
-Dura mater, 58
-Dwarfism, 167
-Dysostosis cleido-cranialis, 167
-Ear, anomalies of, 74
-Ectoderm, 35, 3 8
-Ectopia testis, 153
-vesicae, 144
-Embryo, 15
-age of, 38
-Embryonic axis, 1 7
-disc, 17
-mesoderm, 18
-Encephalocoele, 59
-Endochondrial ossification, 159
-Entoderm, 35, 3 8
-Epibranchial placodes, 7 5
-Epididymis, duct of, 146
-Epiglottis, 99
-Epispadias, 155
-Epoophoron, 148
-Eye, 63
-congenital cystic, 68
-development of, 67
-Eyelids, 66
-Face, 77
-anomalies of, 85
+Td
-Facial cleft, oblique, 86
-Femoral artery, 116
-Fertilization, 24
-Foetal age, estimation of, 39
-Foetal circulation, 128
-Follicular atresia, 8, 20
-Follicle stimulating
-hormone, 20, 23
-Foramen, caecum, 79
-of Majendie, 52
-ovale, 108
-patent interventricular, 108
+Hybrid Tidls
-Gall bladder, 94
-Gartner, duct of, 148
-Genitalia, female, 154
-male, 153
-Genetics, 169
-Genital glands, descent
-of, 151
-Genital glands and ducts, 144
+dd
-Genital system, anomalies
-of, 151
-development of, 150
+Pure Dvj&rfs
-Genitals external, 154
-Germinal epithelium, 5
-Gigantism, 167
-Glaucoma, congenital, 68
-Glycogen, 23
-Gonads, 151
-Graffian follicle, 6
-Gubemaculum, 15 1
-Gut, fore, 75
-hind, 75
-mid, 75
-primitive, 87
-Gynaecomastia, 43
-Haemocytoblasts, 131
+1 1 r
-Hair, 41
-Hare lip, 86
-Haploid number, 13
-Heart, 100
-anomalies of, 108
+Td Td dd TT
-development of, 107
-valves, 106
-Hensenâ€™s node, 17, 18
-INDEX
+i
-Hereditary characters, 168
+d Td dd
-Hermaphroditism, 155
-Hernia, congenital
-inguinal, 153
-Hippocampal gyrus, 57
-Hormone, follicle
-stimulating, 20
-luteal, 21, 23
-Horseshoe kidney, 14 1
-Hyaloid artery, 66
-Hydrochloric acid, 89
-Hydramnios, 34
-Hydrocephalus, congenital, 59
-Hymen, 149, 150
-imperforate, 151
-Hyoid arch, 76
-Hypermastia, 43
-Hypophysis, 54
-Hypospadias, 155
-Imperforate hymen, 151
+k dd All Pure Ow^ris
-Implantation, 26
-interstitial, 28
-Incus, 72
-Infundibulum, 55
-Inferior vena cava, 122, 128
-Interatrial septa, 102
-Interventricular septum, 105
-Intestine, 89
-non-rotation of, 94
+Fig. 42 . - Schematic Table showing Mendelian Inheritance AS APPLIED TO TALL AND DWARF PEAS.
-Intestinal atresia, 93
-Intestinal tract, anomalies of, 93
-Iris, 67
+T = tall ; d = dwarf.
-Kidney, development of, 140
-pelvic, 14 1
+The fundamental genetic laws are based on the experiments of Mendel (1866) on garden peas. Mendel studied the inheritance of a number of characters of this form, of which tallness and dwarfness may be taken as a typical example. If a tall pea and a dwarf pea were cross-fertilised and the resultant peas planted, all of the plants that grew from them were tall. These he called the first filial generation (Fj). These tall cross-bred plants were allowed to produce peas by self-fertilisation, and when such were sown the second filial generation (F a ) showed some plants that were tall and some that were dwarf, in the proportion of three tall to one dwarf. Peas derived from self-fertilisation of each of the dwarf plants were then sown, and they produced dwarf plants only ; seed from some of the self -fertilised tall plants produced both tall and dwarf offspring, in the proportion of three tall to one dwarf ; the remainder of the seed from the tall plants produced nothing but tall offspring in the third (F s ) generation (see Fig. 42 for details).
-Labia minora, hypertrophy of,
-Lachrymal glands, 66
+From these experiments it is clear that an attempt was being made by nature to separate the original pure characters of tallness and dwarfness in the parent stock from the hybrids. This is known as the law of segregation. The character of tallness, which was found in the F x generation, is known as a dominant character since it overshadows the recessive character of dwarfness. These characters are known to be caused by certain elements on the maternal and paternal chromosomes called genes.
-Lactiferous ducts, 43
-Lamina, alar, 48, 51
-basal, 48, 51
-Lanugo, 42
-Lens, 64
-Ligament of Marshall, 122
-Limb muscles, 158
-Lissauerâ€™s bundle, 46
-Liver, 89, 94
+Parents
-anomalies of, 98
+â€” Y
-development of, 97
-Lymphatic vessels and
-glands, 129
-Lymphoblasts, 131
-Malleus, 72
++ dd
-Majendie, foramen of, 7 2
-Mammary glands, 42
-Mandible, 162
-Marshall, ligament of, 122
-Maxillary process, 162
-Meckelâ€™s cartilage, 72
-diverticulum, 93
-Medulla oblongata, 49
-Mendelian laws, 171
-Meninges, 58
-Meningocoele, 59
-Menstruation, 21
-Mesencephalon, 48, 53
-Mesoderm, 35
-extra-embryonic, 19
+P&rent G&mefes
-Mesogastrium, dorsal, 89
-Mesonephros, 136
-Metanephros, 138
-Metencephalon, 49, 52
-Microcephaly, 59
-Mid-brain flexure, 51
-Milk teeth, 80
-Mitosis, 8
-Mucin, 23
-Mullerian duct, 146
+T
-tubercle, 146
-Myelencephalon, 49, 51
-Myelocytes, 131
-Myotomes, 157
-Nails, 41
+Â»
-Naso-lachrymal duct, 41
+d
-groove, 77
-Nerve, abducent, 60, 62
+j 1
-auditory, 60
-facial, 60, 62
-glossopharyngeal, 60, 62
-hypoglossal, 60, 62
-oculomotor, 60, 62
-olfactory, 60
-optic, 60
-trigeminal, 60, 62
+F 1
-trochlear, 60, 62
-vagus and accessory, 60, 62
+.Td
+Fj. Q&metes
-i8o
+_T.
+d. T. d.
-AIDS TO EMBRYOLOGY
+F t T ~ v7~ 1 ' >
-Neuroblasts, 48
+F * TT. Td. Td. dd.
-Neurocranium, 162
-Neuroglia, 48
-Notochord, 35
-Notochordal canal, 17
-Nucleus ambiguus, 51
+Fig. 43. â€” Schematic Table to show Segregation of the Tall and Dwarf Genes in the Gametes of Peas.
-Oesophagus, 88
+T = tall ; d = dwarf.
-Oestrogen, 23
-Olfactory organ, 63
-pit, 77
-tract, 57
-Oligamnios, 34
-Oogenesis, 6
-Optic cup, 63
-Oro-nasal groove, 77
-Ossicles, auditory, 74
-Osteoblasts, 159
-Osteoclasts, 159
-Otocyst, 69
-Ovaries, absence of, 151
-Ovary, 5
-round ligament of, 153
+Consideration of Fig. 43 will indicate how these dominant and recessive factors become separated out during breeding. The parent stock possessed either the character of tallness or dwarfness in pure form, that is, when self -fertilised they always bred true. The first filial generation (Fj) were all tall since the gene for dwarfness was present but masked by the dominant tall (T) gene. The gametes (sex cells) of the Fj generation contained the genes for tallness and dwarfness in equal numbers so that when such plants were self-fertilised the dominant T gene would be present in three out of four of the offspring and they would all be tall plants. In one out of the four, two d (dwarfness) genes would be present and hence these plants would be dwarfs, and on further selffertilisation would continue to breed truly dwarf. One of the three tall plants would contain only genes for tallness and so on self-fertilisation it would continue to breed true for the character of tallness. The remaining two tall plants contained Td genes, and further inbreeding of them would result in the formation of dominant and recessive forms in the ratio of three dominant to one recessive.
-Palate, 78
+In human genetics there are certain clear-cut cases of inheritance due to dominant factors. Examples of these are congenital brachydactyly, syndactyly, and congenital night blindness. Also black hair colour is dominant over brown hair colour, and so is brown iris colour over blue.
-Palatine tonsil, 85
-Pancreas, 95
-anomalies of, 98
-development of, 97
-Paradidymis, 147
-Parathyroids, 84
-Parotid gland, 82
-Paroophorn, 148
-Patent interventricular
-foramen, 108
-Pelvic kidney, 141
-Penis, double, 155
-Pericardial cavity, 132
-Peripheral nervous system, 62
-Persistent foramen ovale, 108
-Pharyngeal region, 75
-anomalies of, 85
-development of, 85
-Pharyngeal grooves, 83
-pouches, 83
-Pharyngo-tympanic tube, 74
-Phimosis, 155
-Pineal gland, 54
-Pinna, 73
-accessory tubercles of, 74
+Mendelian laws have been applied to animals and they have been found to hold equally good for them. For example, the colour of the ordinary brownishgrey wild mouse is due to bands of pigment in its hair ; black at the base and yellow at the tip. This is known as â€œ agouti â€ colouration. But in fancy mice there is a variety in which the hair appears black, due to the absence of the yellow tip to the hair. If a pure agouti mouse is crossed with a black or non-agouti, the offspring at Fj are all agouti in colour â€” that is, the agouti factor is dominant over the non-agouti, which is the recessive factor. If however these hybrids are inbred, the F 2 generation comes out as 25 per cent, pure agouti, 50 per cent. hybrid agouti, and 25 per cent, pure non-agouti. This shows the Mendelian ratio of 1 : 2 : 1.
-Pituitary gland, 54
+In both the agouti (A) and the non-agouti (b) mice there is a variety with straight hair (S) and a variety with wavy hair (w). If a non-agouti wavy mouse (bw) be crossed with an agouti straight mouse (AS), the F! animals will be agouti straight (AbSw) since A is dominant over b, and S over w. Then if these F x hybrids are inbred the genes will be segregated out as follows :
-Placenta, 15, 31
-Placodes, epibranchial, 75
-Plagiocephaly, 167
-Pleural cavities and
-diaphragm, 134
-Polydactyly, 167
-Pontine nuclei, 52
-Prepuce, 155
-Primitive atrium, 100
-ventricle, 100
-Processus vaginalis, 15 1
-Progesterone, 20, 24
-Pronephros, 136
-Pronucleus, female, 13
-male, 12
-Prostate gland, 142
-Pulmonary arteries, 117
-trunk, 105
-Puncta lachrymalia, 68
+Agouti straight (AS) Agouti wavy (Aw) Non-agouti straight (bS) Non-agouti wavy (bw) .
-Rachischisis, 59, 166
-Rathkeâ€™s pouch, 55
-Rectum, malformations
-of, 93
-Reichertâ€™s cartilage, 72
-Rennin, 89
-Respiratory system, 98
-Rhombic lip, 52
-Ribs, supernumerary, 166
+In these experiments two new types have been produced â€” the agouti wavy and the non-agouti straight. The combinations of dominant and recessive characters which have produced these adult forms are shown in Fig. 44. It will be seen that the AbSw hybrids gave rise to four gametes in equal numbers :
-Saccule, 73
+AS : Aw : bS : bw.
-Salivary glands, 82
-Scaphocephaly, 167
-Schlemm, canal of, 66
-Schlera, 66
-Schlerotomes, 161
-Scrotum, 15 1
-Sebaceous glands, 42
-Segmentation nucleus, 13
-Septum, posterior median, 48
-transversum, 36
-Sinus, inferior sagittal, 120
-superior sagittal, 120
-venosus, 100, 105
-Situs inversus, 94
-Skeleton, anomalies of, 166
-Skin, 40
-Skull, 1 61
-Somites, 157
-INDEX
+These combinations take place in the ova as well as in the spermatozoa and since every kind of ovum is likely to be fertilised by any kind of spermatozoon, there are 4 s = 16 possible combinations yielding 9 agouti straight, 3 non-agouti straight, 3 agouti wavy and 1 non-agouti wavy. The several genes of the cross are being segregated out as is shown in Fig. 44. This rule holds good for other possible combinations.
+The blood groups A, B, AB and O are transmitted from parents to offspring in accordance with Mendelian laws. The principles involved may be briefly stated as follows :
-Spermatogenesis, 2, 26
+When red blood corpuscles of one animal species are mixed with the serum of another species they become clumped together or agglutinated. There is in the serum a substance (an agglutinin) which attaches itself to an agglutinable substance (agglutinogen) in the red cells and clumping occurs. In man, blood cannot be transfused from one person to another unless the two bloods are compatible. The important factor is the agglutinogen in the red cells of the donor ; if that is incompatible with the agglutinin in the recipientâ€™s serum, serious consequences will result in transfusion. From the standpoint of heredity the A and the B agglutinogen factors are dominant over the O factor. If a childâ€™s blood belongs to either group A or B one or other of its parents must have blood belonging to such a group.
-Spermatozoon, 4, 26
-Sphenoid, 162
-Spinal cord, 46
-anomalies of, 48
-development of, 47
-Spinal nerves, 59
-Splanchnopleure, 19
-Spleen, 131
-Split tongue, 86
-Spongioblasts, 48
-Stomach, 88
-Stomatodaeum, 36, 77
-Stenosis of aorta, 108
-of pulmonary artery, 108
-Stratum basale, 22
-spongiosum, 21
-Sublingual gland, 82
-Submandibular gland, 82
-Sudoriferous glands, 42
-Sulcus, calcarine, 58
-central, 58
-collateral, 58
-hypothalamieus, 53
-limitans, 53
-terminahs, 79
-Superior vena cava, 128
-Sweat glands, 42
-Syndactyly, 167
-Synotus, 74
-Teeth, decidual or milk, 80
-enamel of, 80
-permanent, 80
-Telencephalon, 48, 55
-Testis, 1, 145
-absence of, 151
-fused, 15 1
-Thalamus, 53
-Theca interna, 7
-Thymus, 83
-Thyro-glossal duct, 79
-Thyroid, 84
-Tomesâ€™ dental fibrils, 81
+AS
-Tongue, 79
-split, 86
-Tonsils, 83
-Trabeculae, 95
-Trophoblast, 15
-Tunica albuginea, 145
+Aw
-Tympanic antrum, 74
+bS
-cavity, 72
-membrane, 73
+bw
-Umbilical cord, 31, 35
+Sperms
-hernia, congenital, 93
-veins, 95
-Urachus, cysts of, 144
+" J t
-Ureter, 140
-double, 1 41
-Ureteric bud, 140
-Urethra, 142
-stenosis of, 155
-Urorectal septum, 141
-Uterine milk, 5, 148
-tubes, 5, 148
-Uterus, 5
-round ligament of, 153
+A5
+A A 55
-\
+Pure Agouti.
+^ure
-Vagina, anomalies of, 151
+Straight.
-Valves, atrio-ventricular, 105
-Vas deferens, 147
-Vasa efferentia, 147
-Veins, anterior cardinal, 119
-posterior cardinal, 122
-anomalies of, 128
-Vena cava, inferior, 105
-superior, 105
-Venous system, 118
-development of, 126
-Villi, 15
+AASw Pure Agouti. Hybrid Straight.
-anchoring, 30
+AbS5
-chorionic, 29
-Viscerocranium, 164
-Vitreous humour, 66
-Vocal cords, 99
+Hybrid Agouti.
-Whartonâ€™s jelly, 35
+Pure
-Witchâ€™s milk, 43
+Straight.
-Yolk sac, I 5 -I 7 , 34 , 99
+AbSw Hybrid Agouti, | Hybrid
+Straight. I
-Zona pellucida, 6,
+Aw
-Zygote, 12
+A A5w
-, 15
+Pure Agouti. Hybrid
+Straight.
+AAww
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+Pure Agouti. Pure Wave.
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+Fig . 44. - Schematic Table to show the possible Combinations of the genes for straight hair, wavy hair, Agouti Colour and Non-Agouti Colour in Mice. A = agouti ; S = straight ; b = non-agouti ; w - wavy.
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+XbX?
-AIDS TO MEDICAL TREATMENT. By T. II. Crozier,
-M. D., D.P.H., M.R.C.P. Second Ed. In preparation .
+Marries
-AIDS TO MEDICAL DIAGNOSIS. By G. E. F. Sutton,
-M.C., M.D., M.R.C.P. Sixth Ed. Pp. viii + 308, with 40
-figs. 6s *
+Son free from Â® AY disease but CANNOT TRANSMIT, normd male.XY
-AIDS TO SURGICAL DIAGNOSIS. By Sir Cecil Wakeley,
-K.B.E., C.B., D.Sc., F.R.C.S., F.R.S. Second Ed. Pp.
-viii + 172, with 6 figs.
-AIDS TO DERMATOLOGY. By R. M. B. MacKenna, M.D.,
+XkY <?
-B Ch., F.R.C.P. Third Ed. Pp. viii + 3Â°9, with 5 figs. 6s.
-AIDS TO DISEASES OF CHILDREN. By F. M. B. Allen,
-M.D., F.R.C.P. Eighth Ed. Pp. viii + 268. 6s.
-AIDS TO NEUROLOGY. By E. A. Blake Pritchard, M.D.,
+T
-M.R.C.P. Pp. viii + 376, with 43 figs. os. 6a.
-AIDS TO OPHTHALMOLOGY. By P. McG. Moffatt,
-F.R.C.S. Eleventh Ed. 6s * 6d *
-AIDS TO PSYCHIATRY. By W. S. Dawson, M.D., F.R.C.P.,
+XwX?
-D.P.M. Fifth Ed. Pp. viii + 306. 6s.
-AIDS TO PSYCHOLOGY. By John H. Ewen, M.R.C.S.,
-M.R.C.P., D.P.M. Third Ed. In preparation.
-AIDS TO TROPICAL MEDICINE. By J. C. Broom, M.D.
+~~\ â€”
-Fourth Ed. Pp. viii + 203, with 30 figs. 5 s.
-AIDS TO TROPICAL HYGIENE. Edited by Lucius
+XX?
-Nicholls, M.D., Third Ed. Pp. viii + 217, with 6 figs. 6 s.
-AIDS TO THE DIAGNOSIS AND TREATMENT OF
-VENEREAL DISEASES. By T. E. Osmond, M.B.,
-M.R.C.S. Pp. vi + 138, with 3 figs. 5s *
+â€œ1
-AIDS TO THE ANALYSIS OF FOODS AND DRUGS. By
+XY o* *
-J. R. Nicholls, D.Sc., F.I.C. Sixth Ed. Pp. via + 424
-I US.
-AIDS TO QUALITATIVE INORGANIC ANALYSIS By
-R. G. Austin, B.Sc., F.R.I.C., F.R.M.S. Second Ed.
-Pp. x + 208, with 9 illustrations. 5s *
-AIDS TO BIOCHEMISTRY. By E. A. Cooper, D.Sc.,
+fUemophi'ic Son. Daughter free Normal Daughter. Normal Son.
-F.R.I.C. Fourth Ed.
-AIDS TO INORGANIC CHEMISTRY. By R. G. Austin,
+from disease but CA N
-B.Sc., F.R.I.C., F.R.M.S. Pp. x + 348, with 6 ngs. 5 s. 6d.
-AIDS TO ORGANIC CHEMISTRY. By S. F. Smith, M.B.,
+TRANSMIT.
-B.S. Third Ed. Revised by Ian Leslie, B.Sc. Pp. vui + 120.
-AIDS TO PHYSICAL CHEMISTRY. By R. G. Austin,
+Fig. 45. â€” Schematic Table to show the Transmission of haemophiliac genes through three generations.
-B.Sc., F.R.I.C., F.R.M.S. Second Ed. In preparation .
-AIDS TO DISPENSING. By G. M. Watson. Fourth Ed,
+X, female chromosome with non-haemophiliac gene ; Xh, female chromosome with haemophiliac gene ; Y, normal male chromosome.
-In preparation .
-STUDENTSâ€™ AIDS SERIES (continued)
+action of a gene or there may be a lethal gene present. An example of the latter is the disease in man called Huntingdonâ€™s chorea. Here the disease appears first about 35 years of age and the patient rarely lives longer than ten to twelve years after that time. The carrier is eventually killed by his or her predisposition to the disease but only after he or she has passed on the lethal gene to the offspring.
-AIDS TO PHARMACEUTICAL LATIN. By G. E. Trease,
+Sex-linked characters are important in certain rare diseases such as haemophilia. The factor here is transmitted on an X chromosome. If a haemophiliac male marries a normal unrelated female all their daughters must necessarily receive one haemophiliac X chromosome from the father and a normal X chromosome from the mother. The sons all receive a normal Y chromosome from the father and a normal X chromosome from the mother. They therefore do not suffer from the disease, nor can they transmit it to their offspring. But the daughters all have a haemophilac X chromosome, and they will necessarily transmit the disease to 50 per cent, of their sons after marriage with a normal male.
-B.Pharm., Ph.C. Second Ed. Pp. vi + 170. 4 s.
-AIDS TO FORENSIC PHARMACY. By M. E. Campbell,
-Fourth Ed. In preparation.
-AIDS TO THE MATHEMATICS OF PHARMACY. By
+==Appendix==
-A. W. Lupton, M.C., Ph.C. Second Ed. Pp. vi + 122. 4 s.
-AIDS TO PHYSICS. By F. J. Jackson, B.Sc., Ph.C., M.P.S.
+===Ossification Times===
-vols. In preparation.
-AIDS TO PUBLIC HEALTH. By Llywelyn Roberts, M.D.,
+The ossification periods have been widely studied, but the work of Hess (i9 2 3)> although differing in some respects from that usually given in textbooks on osteology, is now recognized as being the most accurate series of observations at present available. These observations may be summarized as follows :
-D.P.H. Fifth Ed. Pp. viii 4- 259, with 4 figs. 6s.
-AIDS TO SANITARY SCIENCE AND LAW. Revised by
+th week : Mandible, diaphysis of clavicle.
-William Hanna, M.D., D.P.H. Third Ed. Pp. vi 4- 362.
-s. 6d.
+th week : Diaphysis of humerus, radius, and ulna. 9th week : The terminal phalanges, the 2nd and 3rd basal phalanges, and the 2nd and 3rd metacarpal bones of the hand ; the ilium ; the 2nd and 3rd metatarsals, and the terminal phalanges of the foot bones.
+th week : 1st rib, and the 4th and 1st basal phalanges of the hand.
-OTHER BOOKS
+th to 12th week : 4th, 5th, and 1st metatarsals.
-HANDBOOK OF BACTERIOLOGY. By J. W. Bigger,
+th to 1 2th week : The basal phalanx of the 5th digit, and the middle phalanges of the 2nd, 3rd, and 4th digits of the hand.
-M.D., Se.D.(DubL). Sixth Ed. In preparation.
-BUCHANANâ€™S MANUAL OF ANATOMY. Edited by
+th to 14th week : All the remaining metatarsals and the phalanges of the foot except the last phalanx of the 5th digit.
-F. Wood Jones, D.Sc., F.R.S., F.R.C.S. Seventh Ed. Pp.
-viii 4 - 1616, with 847 illustrations. 45 s.
-ELECTROTHERAPY AND ACTINOTHERAPY FOR
+th to 1 6th week : The middle phalanx of the 5th finger.
-STUDENTS. By E. Bellis Clayton, M.B., B.Ch.
-In preparation.
+6th to 17th week : Descending ramus of ischium.
-GREENâ€™S MANUAL OF PATHOLOGY. Revised by
+th to 20th week : Odontoid process of axis.
-H. W. C. Vines, M.A., M.D. Seventeenth Ed. In preparation.
-A METHOD OF ANATOMY. By J. C. B. Grant, M.B.,
+1st to 24th week : Sternum.
-Ch.B., F.R.C.S. Third Ed. Pp. xxiv + 822, with 729
-illustrations. 33s.
-DISEASES OF THE SKIN. By R. W. MacKenna, M.D.,
+1st to 28th week : Descending ramus of pubis.
-M.R.C.P. Fourth Ed. Pp. xiv + 557, with 214 illustrations. 25 s.
-MAY & WORTHâ€™S DISEASES OF THE EYE. Edited by
+1st to 29th week : Calcaneus (os calcis).
-M. L. Hine, M.D., F.R.C.S. Tenth Ed. In preparation.
-ROSE & CARLESSâ€™ MANUAL OF SURGERY. Edited by
+th to 32nd week : Talus (astragalus).
-Sir Cecil Wakeley, K.B.E., C.B., D.Sc., F.R.C.S., F.R.S.
-Seventeenth Ed. 2 Vols. Vol. I. Pp. xii + 840. Vol. II.
-Pp. iv 4 - 926, with 1130 illustrations. 35 s.
-STEDMANâ€™S PRACTICAL MEDICAL DICTIONARY.
+rd to 36th week : Last phalanx of the 5th digit of foot.
-Edited by N. B. Taylor, M.D. Sixteenth Ed. Pp. xii 41292, with 450 illustrations. 42 s.
+th to 48th week : Distal epiphysis of femur, and occasionally the proximal epiphysis of tibia.
-For further information on these and other Bailliire books, please apply to  the publishers.
+The wide variation in these figures might be accounted for by the statement of Pryor (1927), that ossification begins at an earlier date in female foetuses than in the male.
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Book - Aids to Embryology (1948) 14: Difference between revisions

Latest revision as of 15:54, 25 October 2018

Chapter XIV The Transmission of Hereditary Characters

Appendix

Ossification Times