112 OBSTETRICAL PHYSIOLOGY. 



this material, tlie vessels gradually cease to carry it -, consequently both 

 become atrophied when they cease to grow. 



When the nervous system has arrived at a certain degree of develop- 

 ment, it begins to assume its functions ; though the first manifestations 

 of its activity are very obscure, and probably limited to mere tactile im- 

 pressions, evinced by movements more or less appreciable. It is well 

 known that in the pregnant Mare and Cow, after their ingestion of a 

 large quantity, of cold water, the foetus, towards the end of the second third 

 of gestation, and more particularly in the later months, executes move- 

 ments which are at times so marked that they can be felt if the hand is 

 applied to the abdominal parietes, or even seen in the region of the 

 flank. It is very probable that these automatic or reflex movements may 

 produce torsion of the umbilical cord, and in this way become a predis- 

 posing cause of abortion. Colin, having had occasion to lay open the 

 abdomen of a living pregnant Mare within two or three months of par- 

 turition, saw the foetus, immediately after the incision in the abdominal 

 walls, jumping about in the uterus in a very lively manner without any 

 external stimulus being applied ; it moved the whole of its body, or with- 

 drew its legs or head when pinched through the uterus and the envel- 

 opes. In a quarter of an hour after removal from these and the mother, 

 it no longer moved. The human foetus at five months has been seen to 

 flex and extend its limbs when removed from the uterus. 



Towards the termination of gestation, there can be no doubt that the 

 fcetal movements are somewhat energetic, for at this period the foetus 

 changes its position preparatory to passing through the pelvis. Thus 

 the young soliped, during the whole of its intra-uterine existence, lay 

 with its abdomen turned upwards and the posterior limbs lodged in the 

 largest of the two cornua ; but it now turns over on its belly, with the 

 legs downwards, and the umbilical cord passing across one of its sides. 



The movements connected with deglutition also appear to be performed 

 at an early stage of development, for some of the hairs which are so 

 often observed in notable quantity floating in the amniotic fluid, have 

 been discovered in the foetal stomach. 



Absorption. 



The phenomena of absorption play a considerable part in the develop- 

 ment of the young animal. As soon as the microscopic ovule reaches the 

 uterus, its vitelline envelope or pellucid zone becomes studded with deli- 

 cate, hair-like prolongations — villosities without vessels — which, steeped 

 in the fluid thrown out on the uterine surface, transmit this to the laminae 

 of the blastoderm. At first this absorbent surface is very small, and the 

 growth of the embryo is consequently slow ; nevertheless, this trifling 

 absorption is sufficient to increase. the ovule to forty or fifty times its 

 original volume before the blastodermic laminae and the germinative 

 space are completed. 



Later, when the umbilical vesicle is formed at the expense of the vas- 

 cular and mucous laminae, its vessels absorb the soluble matters that 

 are added to the mass of elements necessary for the growth of the em- 

 bryo. And, finally, when the chorion is at last organized, and furnished 

 with its myriads of vascular papillae in the form of disseminated or ag- 

 glomerated placentulae, absorption goes on with exaggerated activity over 

 the whole uterine surface and texture, in order to supply all the nutrition 

 required for the now rapid development of the foetus. 



