Paper - Conditions of foetal respiration in the goat (1934)
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Barcroft J. Elliott RH. Flexner LB. Hall FG. Herkel W. McCarthy EF. McClurkin T. and Talaat M. Conditions of foetal respiration in the goat. (1934) J Physiol. 83(2):192-214. PMID 16994623
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Conditions of Foetal Respiration in the Goat
By J. Barcroft, R. H. E. Elliott, L. B. Flexner, F. G. Hall, W. Herkel, E. F. Mccarthy, T. McClurkin Anv M. Talaat.
(From the Physwological Laboratory, Cambridge.) (Received July 19, 1934.)
As an introduction to the discussion of foetal respiration it may be desirable to state the essential problem.
(1) In the placenta there is a progressive development of both the maternal and foetal components [Barcroft and Rothschild, 1932; Hammond, 1934].
(2) The maternal components develop on the whole before the foetal ones. Thus in the rabbit by the eighteenth day (the period of gestation being 30 days) the stream of blood through the maternal vessels has attained to at least half its maximum volume. On the other hand the embryos are negligible in size. Therefore the maternal blood rushes through the placenta emerging almost as red as when it entered, the amount of oxygen removed for the purpose of foetal respiration being but trifling}.
(3) From this point as pregnancy proceeds, the embryos grow apace, denuding the maternal circulation of ever-increasing quantities of oxygen. As the quantity of maternal blood which traverses the placenta does not correspondingly increase, that emerging in the uterine veins becomes progressively darker, and at times may be as little as 25 p.c. saturated with oxygen.
(4) In the absence of any special arrangement to the contrary one must picture the placental circulation somewhat as follows:
Two streams of blood enter the placenta by the uterine (maternal) and umbilical (fcetal) arteries respectively. The former is the red arterial blood of the mother, the latter is the dark venous blood of the foetus. In the placenta they come into intimate contact but never actually mix. The limiting condition therefore is that they should emerge in equilibrium, in which case the oxygen pressure in the blood of the umbilical vein (going to the foetus) and that of the uterine veins (returning to the mother) should be sensibly the same. That being so, and again in the absence of any special mechanism to the contrary, one might expect the hemoglobin in each to be of the same percentage saturation and the blood in the two vessels to be similar in colour; neither so red as that in the uterine artery nor so dark as that in the umbilical artery.
1 The above statements are based on the paper of Barcroft, Herke] and Hill [1933].
As their preparation involved injury to the nerves of the uterus the work has been repeated on preparations not open to this objection. The result was the same.
Fig. 1. Superior limit of estimations of percentage saturation of blood in umbilical vein.
Moreover, on the above premises one would expect the blood in the umbilical vein to become progressively darker as pregnancy runs its course.
(5) In fact these expectations are not realized, and towards the end of pregnancy the blood in the umbilical vein is often definitely brighter in colour than that in the uterine veins. Indeed in the goat up to the 19th week of pregnancy the saturation of the blood reaching the foetus tends to become higher (Fig. 1) and that returning to the mother becomes lower. What is the explanation?
(6) Having stated the problem in its general form, some matters of detail may now be mentioned. Paragraph No. (4) above commences,
“In the absence of any special arrangement.” In the rabbit the anatomical structure of the placenta appears to afford at all events a partial explanation, for according to Mossman [1926] the capillaries in the placenta are so disposed that the blood entering the placenta from the foetus makes its first contact with the maternal blood which is about to leave the placenta, whilst the blood leaving the placenta for the fostus makes its last contact with the maternal arterial blood reaching the placenta from the arteries of the mother (Fig. 2a).
With such an arrangement clearly the blood in the umbilical vein could be much redder than that in the maternal vein. But this disposition of vessels appears to be a special feature in certain animals only, and therefore it is not a solution of the general problem.
Fig. 2. Schematic representation of vessels in placenta (a) of rabbit. as described by Mossman, (b) of goat. A, artery carrying blood from mother; B, vein returning blood to mother; C, umbilical vein carrying blood to foetus; D, umbilical artery carrying blood to placenta.
Table I gives data of the age and weight of the foetuses and mothers respectively in the goat. From it growth curves may be constructed as has been done by Huggett [1934] for some of the data given in the table. When the weight of the foetus is plotted against its age a curve of a sigmoid type is obtained. It presents the general appearance to be expected for the growth of an organism which, starting as something very small but growing rapidly, grows at a decreasing rate and ends up as a large organism of slow growth.
Actually the curve when analysed presents some special features. The whole embryo grows from a cell the weight of which is perhaps one millionth of a milligram (i.e. ten times the weight of a red blood corpuscle). If it grew at a uniform rate of sixty-fold increase per week the embryo would be of the order of size which we find it—9 g. at the end of the seventh week. Presumably the growth is more rapid at first and FQ@TAL RESPIRATION IN THE GOAT. 195
TABLE I. Age of foetuses Weight of Serial Weight Date of weeks and Number of foetuses No. kg. operation days foetuses kg. 1 32 22, xii. 32 10 2 0-115 0-110 2 40 5. i. 33 12} 2 0-255 0-275 3 28-4 10. ii. 33 16.3 2 1-25 1:19 4 _ 23. iii. 33 7 1 0-009 5 oo 1. iv. 33 Not pregnant 6 _ 11. iv. 33 10.1 1 0-090 7 _ 13. iv. 33 ll 1 0-160 8 31-2 18. iv. 33 12 2 0-278 0-254 9 23-1 24, iv. 33 13.2 1 0-374 10 25:8 1. v. 33 14.3 1 0-646 ll 36-9 5. v. 33 15.1 2 0-73 0-69 12 _— 12. v. 33 16.1 1 1-225 13 24-6 18. v. 33 Not pregnant 14 37-8 22. v. 33 18 2 1-84 1-43 15 _ 31. v. 33 19.6 1 2-00 16 _— 31. v. 33 *15-16 1 0-900 17 38-8 31. xii. 33 9.5 1 0-075 18 26-2 22. i. 34 12.5 2 0-228 0-251 19 48-8 1. ii, 34 14.5 2 0-563 0-538 0-833 21 40-4 16, ii, 34 19.3 3 0-960 0-952 22 44-8 19. ii, 34 20.4 2 2-28 2-91
Inferred from weight. TaBLe II, Kids. . Date of Serial —_-so_,__—- Weight No. Operation “Stocking” Birth Age kg. 20 5. ii, 34 6. ix. 33 4. ii. 34 20 hours 4:8 23 1. iii, 34 1. x. 33 28. ii. 34 1 day 2-34 26 2. iii, 34 1. x. 33 2. iii, 34 Less than _ . 14 hours
slows down, but it is not surprising to find that in the eighth week the rate of growth is approximately 120 p.c. reckoned in the following way:
if ais the weight at the end of the seventh week and b is the weight at the
end of the eighth week, {7-*) x 100=120. Beginning at the end of the ninth week and continuing to the end of the sixteenth week there is a period during which the rate of growth is almost uniformly 40 p.c. of the weight of the foetus. The rate then becomes slower and at last negligible (Fig. 3).
Another interesting relationship is that of the foctal weight to that of the placenta. Fig. 4 shows this relation for the foetuses other than triplets. We have never had a case of more than three foetuses.
The first point to be investigated regarding the conditions which govern foetal respiration is clearly the exact forms of the oxygen dissociation curves of the maternal and foetal bloods respectively. Two sets of observations on this subject are to be found in the literature. Huggett [1927] reported that the blood of the foetus contained less oxygen at given pressures than that of the mother: his observations were made upon goats. Haselhorst and Stromberger [1930, 1931], in an elegant research on the human subject, came to the opposite conclusion. In neither case, however, was the dissociation curve delineated in detail over the whole of its course, nor was it followed progressively during the period of pregnancy. We were fortunate in obtaining from a reliable source a sufficient supply of goats to obtain weekly information from the seventh week onwards, the period of gestation in the goat being 21-22 weeks.
Method
The goat was anesthetized with urethane 4 c.c. per kg. If necessary it was given some C.E. mixture. The animal was then placed in a saline bath and the abdomen was opened. The foetal blood for analysis was withdrawn from the umbilical artery or vein (as the case might be) with a hypodermic syringe. The syringe was prepared by filling the dead space with a solution of 3 g. acid potassium oxalate and 1 g. sodium fluoride in 100 c.c. water. | Enough of this mixture was placed in the syringe to insure that the blood when drawn would be diluted with the solution in the ratio of 9:1. This may conveniently be done by the use of a syringe, with a glass bead of suitable size to ensure thorough mixing.
The samples of blood for determination of the dissociation curves were drawn as described above and were placed in a saturator filled with air to which CO, was added to a partial pressure of about 50 mm. Hg. 22
Fig. 3. Abscissa, foetal age in weeks. Ordinate, left-hand scale weight of foetuses in kilos, refers to unbroken line; right-hand scale the increment of weight in any week expressed as a percentage of the mean weight for the same week. 500 400 ° L st V 200) 100 Z ez ° | 44 | +" 0 8 9 10 Il 12 13 14 15 16 17 18 19 20 21 Fig. 4. Abscissa, foetal age in weeks. Ordinate, weight of foetus
expressed as a percentage of the weight of the placenta,
The equilibration was carried out at 38°C. in the new saturators [Barcroft, 1934]. The blood-gas analyses were made in the van Slyke manometric apparatus. Usually the determination of a single point required the cooperation of four persons, the gas analysis being done in duplicate by two of them, and the blood-gas determination (also in duplicate) by the others. The maternal blood was equilibrated in saturators of about 300 c.c. capacity. The pipette used delivered two blood samples, each of 1 c.c. The saturators used for the foetal blood were varied according to the size of the foetus, 7.e. according to the amount of blood available. Usually, however, they were of 25-60c.c. capacity, the pipette delivering 0-2 ¢c.c. samples. The curves, both maternal and foetal, were determined in the presence of 50 mm. CO, as nearly as possible, and corrected to that figure. Naturally the smaller the saturator the more difficult it is to hit off the exact CO, reading desired.
Care was taken to put the blood into the van Slyke apparatus immediately it was taken from the bath and not to leave it standing in the pipette. The following is a series of readings showing a fair sample of the accuracy obtained with the foetal bloods using the small tonometer saturators:
Goat 14,
Oxygen pressure Percentage
mm. Hg. saturation (1) 16-2 22-5 16-7 22:3 (2) 24-4 52-6 24-8 52-4 (3) 32-8 80-0 33-1 81-8 (4) 57-2 83-3 57-0 83-7
The chief points about the dissociation curves are as follows.
Fig. 5 shows an area between two dotted lines. These are the limits of the curves which we have plotted for normal female goats, i.e. goats which are not, and have not recently been pregnant. We have ascertained that (1) the curve is not appreciably altered by the anesthetics which we have used, (2) the points fall on the same curve whether the blood is defibrinated by whipping or drawn into a syringe with a tenth of its volume of oxalate fluoride mixture, and (3) the sample of blood gives points on the same curve whether equilibrated in the large or the small saturators.
Fig. 6 (goat 4, seven weeks pregnant) shows the points obtained from the earliest pregnant goat which we studied, and they are all within the normal area,
Fig. 5. Limits within which fall the oxygen dissociation curves of normal female goats not recently pregnant. CO, pressure 50 mm., temp. 38° C.
Fig. 6. Goat 4, pregnant 7 weeks; points on dissociation curve of mother.
Fig. 7. Goat 1, pregnant 10 weeks. e maternal blood; x foetal blood, CO, pressure 50mm., temp. 38° C.
Fig. 8. Goat 6, pregnant 10 weeks 1 day; notation and conditions as in Fig. 7. FQ@TAL RESPIRATION IN THE GOAT. 201
Figs. 7 and 8 show maternal curves (10 weeks and 10 weeks 1 day). They are now definitely to the right of the normal area. One point only in each case has been obtained for the foetal blood; it lies within the normal maternal area.
Fig. 9 (11 weeks and 2 days) shows the maternal blood much as in Figs. 7 and 8, but two points were obtained for the foetal blood. These show a new feature, namely that they lie on a curve which tends to cross the normal area. A single case of this kind might naturally be discounted on the ground that one or other observation was erroneous; its importance, however, is evident from the fact that all the foetal curves up to Fig. 15 show the same characteristic.
Fig. 10 (13 weeks 3 days) again shows a new character, namely that the foetal curve is drifting farther away from the maternal one, as the pressure becomes lower.
For instance, at half-saturation the gap between the maternal and foetal curves in Fig. 9 corresponds to 7 mm. pressure: in Fig. 10 it is 10 mm. or estimating in terms of the difference of saturation at a given pressure, in the same region:
Maternal Feetal blood blood Mean Difference
Percentage saturation: Fig. 9 43 56 493 13 » 10 40 59 494 19
Fig. 11 (14 weeks and 1 day) shows much the same features as Fig. 10 (13 weeks). In the region of 50 p.c. saturation the difference is 17 p.c. The maternal and foetal curves are both more to the right than in Fig. 10. To this we ascribe no special significance, it probably means that before pregnancy the curve in the case of goat 10 (Fig. 11) was near the right of the normal area and that of goat 9 (Fig. 10) was near the left.
In Fig. 12 (15 weeks and 2 days) the gap between the footal and maternal curves has increased and now corresponds to difference of saturation of 25 p.c. at 31 mm. oxygen pressure.
This may be a suitable point to emphasize the relative properties of the maternal and foetal curves which are found at this stage: all our estimations of the percentage saturation of oxygen in the blood of the umbilical vein, 7.e. the foetal blood leaving the placenta, show a considerable degree of unsaturation. They vary very much, which perhaps indicates that the last word has not yet been said as regards technique, but broadly speaking they lie between 80 and 40 p.c. (see Fig. 1) saturation, which is roughly the region covered by the foetal curve in Fig. 12. What then is the difference of oxygen saturation between foetal and maternal blood at a given pressure as one passes down the foetal curve?
Fig. 9. Goat 7, pregnant 11 weeks 2 days; notation and conditions as in Fig. 7. Fig. 10. Goat 9, pregnant 13 weeks and 3 days; notation and conditions as in Fig. 7.
Fig. 11. Goat 10, pregnant 14 weeks 1 day; notation and conditions as in Fig. 7. Fig. 12. Goat 11, pregnant 15 weeks 2 days; notation and conditions as in Fig. 7.
Oxygen pressure mm.
50 37 30 25 21
Saturation of 80 70 60 50 40 foetal blood Difference of O, 8 20 26 28 25
saturation between
maternal and
foetal blood . Thus down to a low point (that at which the dissociation curve of the mother begins to curl inwards towards the origin) the lower the oxygen pressure at which the maternal blood yields its oxygen the greater the amount which can be transferred to the foetus at a given pressure.
At this point we may suitably consider Figs. 13 and 14. They are the dissociation curves of two goats which were members of the series and were operated upon on the assumption that they were pregnant but which in point of fact contained no embryos—that of Fig. 13 had gone 17 weeks from “stocking,” Fig. 14 had gone 9 weeks. The points obtained in both cases fell in, or on the edge of, the area for normal goats. Whether these animals never were pregnant or whether they had contained foetuses which had been reabsorbed, we do not know. They appeared to us to be rather satisfactory controls.
We may now pick up our survey of the general progress of events, which we had brought up to the fifteenth week. Goat 3 (Fig. 15) had gone 16 weeks and 3 days. In its essential points the curve does not differ from that of Fig. 12.
Fig. 16 (18 weeks and 2 days) shows a remarkable change. The dissociation curve of the foetus is altering in shape. The general nature of the alteration is in the direction of increased adaptability to take up oxygen at high oxygen pressures, and this without any sacrifice at low ones (20 mm. and the like). The question may be asked, what does the foetus gain by this increased ability to take up oxygen at low oxygen pressures? A partial answer may perhaps be found in Fig. 1. None of our observations has given us more solicitude than those of the direct records of the percentage saturation of the blood taken from the umbilical vein. The results vary greatly, but the curve shown in Fig. 1 gives the upper limit. Often the points are much lower. At present we have not sufficient information fruitfully to discuss whether these lower observations are due to experimental procedure, e.g. constriction of the uterine vessels when Fig. 14. Fig. 13. Goat 13, not pregnant 17 weeks from presumed fertilization; notation and con. ditions as in Fig. 7. Fig. 14. Goat 5, not pregnant 9 weeks from presumed fertilization; notation and conditions as in Fig. 7.
Fig. 15. Goat;3, pregnant 16 weeks 3 days; notation and conditions as in Fig. 7.
Fig. 16. Goat 14, 18 weeks 2 days; notation and conditions as in Fig. 7. FQ@TAL RESPIRATION IN THE GOAT. 207
the uterus is opened. The highest ones seem to be as high as is consistent with the existing anatomical conditions in the placenta of the goat (see Fig. 26). It is not easy (short of some form of oxygen secretion) to see that the oxygen pressure in the blood which leaves the placenta for the foetus can be much higher than that which leaves the placenta for the mother. If then in goat 14 the curves for the mother and foetus are substantially as in Fig. 16, and if the foetal blood is 83 p.c. saturated, that would correspond to a pressure of 50 mm. O,. This pressure indicates a saturation of 60 p.c. or over in the blood of the uterine vein, which is as high as can be expected, perhaps higher.
These considerations, with some others of a like nature, form as we have said “a partial answer,” but it is difficult to escape the feeling that there is something prophetic about the change in the shape of the dissociation curve. It is acquiring the degree of inflection typical not of foetal but of ante-natal existence. Indeed the eighteenth week is a period at which many alterations take place. Fig. 3 indicates that about this time the embryo ceases to grow at a uniform rate, and the dissociation curve takes on its ultimate degree of inflection whilst the blood in the umbilical vein reaches its maximum saturation (Fig. 1). It is natural to ask, why is the foetus not born at this point? Why does it carry on a lingering existence in the uterus, growing at a reduced rate and straining the conditions of respiration till the blood which supplies it is not 80 p.c. but perhaps 50 p.c. saturated? The answer is probably to be found in the extent to which three or four extra weeks of intra-uterine life enables the newly born kid to fend for itself. On the day that it is born it can walk. At a stage of maturity probably corresponding to the eighteenth week in the kid, the human foetus is born.
The curves for goat 21 (19 weeks and 3 days) do not differ in any essential point from Fig. 16. It happens that the maternal and foetal curves are a little to the left of their position in Fig. 16, but this is probably unimportant, the relation of the curves to one another is essentially the same, but in Fig. 18 (goat 22, 20 weeks and 4 days) there is a marked change. The maternal and foetal curves are drawing towards one another: the conditions are becoming less favourable to foetal respiration at a time when the embryo is still growing and requiring more oxygen. It is not surprising then to find a large drop in the percentage saturation of the blood in the umbilical vein of goat 22 as compared with goat 21 (Fig. 1). But the curves draw still closer. Fig. 19 (goats 25 and 26) shows those of the mother and kid at the birth of the latter which took place after a pregnancy of 21 weeks and 4 days. The birth occurred during the night P.c. saturation with oxygen
Fig. 17. Goat 21, 19 weeks 3 days; notation and conditions as in Fig. 7. Fig. 18. Goat 22, 20 weeks 4 days; notation and conditions as in Fig. 7.
0 10 20 30 40 50 60 Oxygen pressure, mm. Hg Fig. 20.
Fig. 19. Goat 25, and its kid 26 at birth; notation and conditions as in Fig. 7.
Fig. 20. Goat 25, and its kid 26, 18 days after birth; notation and conditions as in Fig. 7. PH. LXXXIII. 14 210 J. BARCROFT AND OTHERS.
and the blood was withdrawn at 10 a.m. next morning so that the exact age of the kid in hours from birth is not known. This picture is of interest as showing the same general features as those figured by Eastman, Geiling and de Lawder [1933] for man, 7.e. a gap between the maternal and foetal curves, the maternal curve definitely to the right of the normal, foetal curve not definitely to the left of the normal and both of the normal degree of inflection.
The curves of goats 25 (mother) and 26 (kid) were determined again 18 days later (Fig. 20); by that time they were indistinguishable—though both to the right of the normal area, possibly because they were both rather anemic.
We have had the opportunity of determining the curves of two other kids, which were sent to us by Mr T. R. Egerton, the well-known breeder of pedigree goats at Rushmere, Ipswich. We would like to take this opportunity of thanking him for the very great trouble he has taken in diverting his organization from its usual business to that of securing that kids born on his farm were in our hands at the earliest possible moment. In the case of kid 20 (Fig. 21) the data for the curve were obtained about 20 hours after birth and before the kid had been fed, while in the case of kid 23 (Fig. 22) the curve was obtained on the day after birth, the kid having had milk. In both these cases the curve had the adult degree of inflection but was slightly to the left of the normal area. Having stated the facts something must be said about the mechanism which lies behind them. This can be treated very shortly because already, both in the case of the maternal and foetal bloods, researches in this series have been published dealing with the matter not merely in a general way but with the actual goats under discussion. There is no element of doubt therefore as to the legitimacy of transferring results obtained upon one species or even one individual to another.
The cause of the shift in the maternal blood is simple; it is due to increased hydrogen-ion concentration. The pH was calculated from CO, dissociation curves by A. B. Keys [1933, 1934], and similar curves from which the pH may be calculated are given by Eastman, Geiling and de Lawder [1933]. The hydrogen-ion concentration was also measured directly with the glass electrode, by Dr R. E. Havard and Mrs S. Dickinson. The table on p. 212 is quoted from Keys’ paper [1934]. Thus the maternal bloods taken during experiment ranged in pH from 7-22 to 7-33, whilst controls taken under similar circumstances, after some considerable period of anesthesia, were 7-35 and 7-41 respectively. These results agree in general with those of Eastman, Geiling and de Lawder [1933]. P.c. saturation with oxygen
100, . 90 an 7 2 4 uo 80 Vs “7 7 7 7 7 4 J / 70 7 17 / / / / / /_/ 60 7—T / / ard ‘ w / 50: ii 7 I / 1 / / / f L 40 Tet 7 / io , 7 0 if 100 30 40 50 60 hod ‘7 N/ 1 / 20 A 90 y Ji a ie “ x, 7 ve 10 C2 an pe 7 7 “ 7 Ce 7 4 4? / vy 7 7 510 20 30 © i 1/ / Oxygen pressure, mm. Hg | j Jo 7 Fig. 21. 60) a / / , of [ : A 7 L / 7 7 7 g rye o / / a0 to Be / L. i ° 40 / * 7 aq toy ® // = / / a ¢ & 30 / ad 2 iy 3 7 5 \/ 2 LV. 8 20 7 7 Ay v/ 4+ 10 M 7 47 “47 ye yo 0 10 20 30 40 50 60
Oxygen pressure, mm, Hg Fig. 22. Fig. 21. Goat 20, 20 hours old; notation and conditions as in Fig. 7. Fig. 22. Goat 23, 1 day old; notation and conditions as in Fig. 7. 14—2
Whilst the divergence from the normal of the dissociation curve in the maternal blood is accounted for by change in reaction, that of the foetal cannot be so explained. In the cases quoted above the foetal bloods,
Blood hydrogen-ion concentrations at 37° C. pH observed by
pH Havard and Goat No. Blood calculated Dickinson 11 Maternal 7-26 7-26 Fetal 7-34 7-38 12 Maternal 7-22 7-25 Fetal 7-30 7-31 14 Maternal 7:23 7-14 Feetal 7-27 7-30 16 Maternal 7:33 7-33 Fetal 7°35 7:34 Control C, Before anesthesia 7:37 15 min. after 7-31 75 min. after 7°35 Control 13 7-35 Control Before anzsthesia 7-50 90 min. after 7-41
whether estimated by the glass electrode or by the CO, method, fall within the pH range 7-27-7-38. Though more alkaline than the maternal bloods they are not more alkaline than the normals. Moreover, the position of the foetal curve is associated with a greater or less difference from the normal in the inflection of the curve.
The position and shape of the foetal curve are governed by conditions other than the hydrogen-ion concentration. The pH indicates greater alkalinity in the foetal than the maternal plasma, but the foetal plasma is not more alkaline than that of the normal controls. Moreover, a change in the hydrogen-ion concentration would not in itself produce the less S-shaped type of curve which is portrayed especially before the eighteenth week.
Two researches have been carried out on this subject, by McCarthy [1933] and Hall [1934a, 19346] respectively. The former liberated and purified the hemoglobin from the animals used in several of the experiments already quoted. He found that, working with the purified hemoglobin, the curves for the maternal pigment were indistinguishable, under identical conditions, from those of the controls. Those from the fcetal blood, however, were definitely to the left, over the major portion of the curve. The only thing to be added to McCarthy’s published work is that, since his paper was written, he has investigated the hemoglobin of a kid, which he found to be like that of a normal goat and therefore unlike the hemoglobins of the foetuses. FQ@TAL RESPIRATION IN THE GOAT. 213
The general coincidence between data obtained from purified hemoglobin by McCarthy and data obtained from blood by ourselves is well shown in Fig. 23. In Fig. 23(a) we give McCarthy’s points for goat 12 (16 weeks 1 day) as accurately as we can read them from curves 2 and 3, Fig. 1 of his paper, together with our curves for the blood of the same goat, while the points for goat 14 (18 weeks), taken from his curves 4 and 5, are similarly shown in comparison with ours in Fig. 23(b).
9 20 40 60 80 % 20 40 60 80
(a) Oxygen pressure, mm. Hg (6)
Fig. 23. (a), goat 12; (6), goat 14. co McCarthy maternal hemoglobin, pH 6-8; o McCarthy foetal hemoglobin, pH 6-8; x foetal blood CO,=50 mm.; e maternal blood CO,= 40 mm.
The dissociation curves proper to the hemoglobins of the mother and foetus respectively have also been investigated by Hall [1933, 1934a, 19346] by the method which he recently described. The investigation, unlike that of McCarthy, was on dilute solutions and by spectroscopic methods, but the result was essentially the same, namely that the foetal curve was to the left of the maternal and on the whole less inflected, though not actually hyperbolic. Hall [1934c] has also found differences between the hemoglobins of the embryo chick and its mother similar to those which he observed between the foetal and maternal hemoglobins in goats and rabbits.
Summary and Conclusions
- The problem of foetal respiration is that of an organism growing in mass, at a much greater rate than the machinery for its supply.
- Oxygen dissociation curves are given for the blood of the mother and the foetus, making a complete series from about the tenth week till birth.
- The curve of the mother moves to “the right” of the normal, that of the foetus being for the most part to the left.
- The maximum divergence is about the eighteenth to nineteenth week, after which the curves draw together.
- The movement on the part of the curve of the mother is due to increased hydrogen-ion concentration.
- The foetus contains hemoglobin, the properties of which differ from that of the mother. It gives a less inflected curve, as well as one which is situated “to the left” of the normal.
- So is explained the gap between the maternal and foetal dissociation curves noted by other observers [Haselhorst and Stromberger, 1930; Anselmino and Hoffmann, 1931; Eastman, Geiling and de Lawder, 1933].
We should like to thank Mr G. S. Adair for valuable help given from time to time.
References
Anselmino, J. and Hoffmann, F. (1931). Arch. Gyndk. 147, 69.
Barcroft, J. (1934). J. Physiol. 80, 388.
Barcroft, J., Herkel, W. and Hill, R. M. (1933). Ibid. 77, 194.
Barcroft, J. and Rothschild, P. (1932). Ibid. 76, 447.
Eastman, N. J., Geiling, E. M. K. and de Lawder, A. M. (1933). Johns Hopk. Hosp. Bull. 58, 246.
Hall, F. G. (1933). Quoted by Barcroft, Lancet, Nov. 4, 1933, p. 1021.
Hall, F. G. (19340). J. Physiol. 80, 502.
Hall, F. G. (19346). Ibid. 82, 33.
Hall, F. G. (1934c). Ibid. 88, 222.
Hammond, J. (1934). Verbal communication.
Haselhorst, G. and Stromberger, K. (1930). Z. Geburtsh. Gyndk. 98, 49.
Haselhorst, G. and Stromberger, K. (1931). Ibid. 100, 48.
Huggett, A. St G. (1927). J. Physiol. 62, 373.
Huggett, A. St G. (1934). In the Press,
Keys, A. B. (1933). Quoted by Barcroft, Lancet, Nov. 4, 1933, p. 1021.
Keys, A. B. (1934). J. Physiol. 80, 491.
McCarthy, E. F. (1933). J. Physiol. 80, 206.
Mossman, H. W. (1926). Amer. J. Anat. 37, 433.
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