76 OBSTETRICAL PHYSIOLOGY. 



the end of gestation the albumen diminishes. Probably the formation of 

 the mucus covering that invests the young animal at birth, is due to the 

 precipitation on its skin of the mucus and yellow matter contained in this 

 fluid. Hoppe-Seyler gives its chemical composition as water, holding in 

 solution a small quantity of casein, kreatin, lactic acid, grape sugar, and 

 saline matter ; and therefore resembling very dilute serum. 



The uses of the liquor amjiii are varied and important. It is not very 

 probable that it serves as nutriment for the foetus in the early period of 

 intra-uterine life ; though it has been found in the stomach of those young 

 animals which had been purposely frozen in their membranes, and then 

 dissected ; portions of the hoof epithelium have also been discovered in 

 the foetal stomach. It preserves an equable temperature for the young 

 creature ; maintains the integrity of its exterior before the skin is covered 

 by the peculiar sebaceous coating ; favors its movements and its devel- 

 opment, by removing it from unequal pressure ; diminishes the impres- 

 sion from sudden external movements and shocks, thus preserving it from 

 injury ; and allows it to obey the laws of gravitation. It also protects 

 the mother from injury by the foetus, towards the termination of gesta- 

 tion. During parturition, it protrudes the membranes ; is the primary 

 agent in dilating the os uteri ; shields the foetus from the direct action of 

 the uterine contractions, whose violence might compromise its existence ; 

 renders the dilatation of the os easy and prompt ; and finally, by lubrica- 

 ting the vagina, causes the passage of the foetus through it to be more 

 gentle and expeditious than it would otherwise be. 



Differences in the Amnion of other Animals. 



Ruminants. 



The amnion in Ruminants is similar to that of the Mare. It is easily 

 separated into two layers, and shows on its inner surface, particularly 

 near where it invests the umbilical cord, a large number of white or yel- 

 lowish-white bodies. In the Cow these are sometimes elongated in 

 the form of papillae ; at other times they exist in flattened, slightly 

 raised patches, about one-fourth of an inch long. Sometimes they are 

 single; occasionally they are in clusters. They consist of large, flat, 

 nucleated cells, resembling a squamous epithelium ; it is concluded that 

 they are the seat of formation of a glycogenic material. Up to a certain 

 period of intra-uterine life, they increase in size and then degenerate : 

 their organization and development being in inverse relation to the 

 development of the liver, whose function they assume, with regard to 

 glycogenation. Externally the amnion is altogether in contact with the 

 allantois and chorion. 



Pig. 

 It does not differ in the Pig. 



Bitch and Cat. 



In the Bitch and Cat the amnion is entirely covered by the amniotic 

 layer of the allantois, to which it adheres in the same manner as in the 

 Mare ; the two membranes are only separated by the umbilical vesicle, 

 and there is no trace of the pouch and vascular plexus seen in that animal. 

 In the amniotic liquid, crumbs of meconium are found towards the end 

 of gestation. 



