CHANGES IN THE O VUM. i j 5 



life, and which has been adverted to, it is seen that the chief propelling 

 power is centred in the right side of the heart ; the force of the left heart 

 being mainly spent in effecting a due supply of blood to the head and 

 upper extremities. And the structure of the heart proves this to be the 

 case, for the walls of the right ventricle have been found as thick as those 

 of the left ; while the walls of die right auricle are even thicker and more 

 muscular than those of the left auricle : a condition which persists for a 

 short time after birth. 



The isolation that exists in the two circulatory systems, might lead to 

 the inference that there was no relation between the contractions of the 

 heart in the foetus and those of the maternal organ, and experience proves 

 this to be the case. Naegele has noted that there is no relation between 

 the beats of the heart of the human foetus and those of its mother's heart. 

 By auscultation he was able to distinguish the two sounds of the foetal 

 heart, and found it beat on an average 135 times per minute : never more 

 than 180, nor less than 90; and he remarked that the beats were sensi- 

 bly the same from four and a half months, when they are first perceptible, 

 until birth. And Hollmann, in resorting to the same mode of investigation 

 in Cows, ascertained that, in one which was advanced eight and a half 

 months in pregnancy, and whose pulse was 64 per minute, the foetal beat 

 was 124 ; in another Cow, but which was ill, the pulse was from 70 to 

 112, while that of the foetus was 113 to 128. 



Colin opened a living Mare which had been pregnant for nine or ten 

 months, and a Cow whose gestation dated about three months. When 

 the uterus of the Mare was opened, and the contained envelopes incised 

 to extract the foetus, the latter moved actively and respired deeply, though 

 at rare intervals. The umbilical arteries and vein yielded some blood, 

 from the small punctures made through their walls ; the first throbbed 

 with a certain amount of force, and the pulsations were rapid. When the 

 cord was divided and tied, the foetus appeared to be dead : there were no 

 more spontaneous movements, and the respiration had ceased. The tho- 

 rax and the abdomen were now thrown open, and it was observed that 

 the heart contracted spontaneously arid strongly, and the pulsations of 

 the aorta and umbilical arteries could be very distinctly felt. At first the 

 contractions of the auricles regularly alternated with those of the ventri- 

 cles, as in a normal condition ; but soon, as occurs in expiring animals, 

 the auricles contracted several times for one contraction of the ventricles, 

 as if it required several systoles of these to fill the ventricular cavities. 

 At each contraction the auricles diminished much in volume, became 

 nearly empty, and looked very pale, but assumed their reddish-violet 

 color again during their diastole. At last the rhythmical movements be- 

 came altogether perverted ; the auricles and ventricles contracted simul- 

 taneously and quickly, but more and more feebly, and finally ceased alto- 

 gether half an hour after the thorax had been opened. The Cow in 

 which the foetal circulation was studied, had its flank wddely incised, and 

 one of the cornua of the uterus withdrawn through the opening. Some 

 of the placentulae were removed with difficulty from their cotyledons, and 

 both bled a good deal. When the umbilical cord was exposed, the beat- 

 ing of its very tense arteries could be distinctly felt ; and when com- 

 pressed, these enlarged between the foetus and the point where the pres- 

 sure was applied. On removing the foetus from the uterus, it did not 

 make any perceptible movement, but then it was only three or four 

 months old. The thorax having been opened, the action of the heart 



