120 OBSTETRICAL PHYSIOLOGY. 



growth goes on concurrently. If the vessels do not carry a sufficient 

 supply of formative material, the development of the part is tardy or 

 ceases ; and, on the other hand, if the latter from some cause becomes 

 feeble and cannot assimilate this material, the 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 

 impressions, 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 movements 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 predisposing cause of abortion. Colin, having had occasion 

 to lay open the abdomen of a living pregnant Mare within two or three 

 months of parturition, 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 withdrew its legs or head when pinched through 

 the uterus and the envelopes. 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 

 foetal 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 per- 

 formed 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 

 delicate, hair-like prolongations — villosities without vessels — which, 

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

 the lamina of the blastoderm. At first this absorbent surface is very 

 small, and the growth of the embryo is consequently slow ; neverthe- 

 less, 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 

 vascular and mucous laminee, its vessels absorb the soluble matters that 

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



