400 THE PHYSIOLOGY OF REPRODUCTION 



time this part of the mucosa shows signs of great degenera- 

 tion , resembling the pulpe diffluente of Duval in the guinea-pig 

 (Assheton). The inter-glandular cells also hypertrophy like the 

 connective tissue cells of Rodents. 



The inter-cotyledonary trophoblast is avillous in the sheep 

 and cow. In the giraffe, however, there are rows and clusters 

 of villi in addition to the cotyledonary villi. 



The development and structure of the placenta of the sheep 

 have been described at some length because the formation of 

 the special nutriment for the foetus has received close atten- 

 tion in that animal. 1 



Cow. In the cow (Fig. 92) the placenta has essentially the 

 same form as in the sheep, but the interlocking is not so firm. 

 On separation of the maternal and foetal parts of the cotyledons, 

 the former are found to comprise the larger part. In the 

 fully developed sheep's placenta the foetal parts constitute the 

 main mass of the cotyledon. The various stages of develop- 

 ment have not been completely investigated, but one other 

 difference has been noted, viz. the absence of lacunae of maternal 

 blood at the bases of the villi (Ledermann 2 ). 



The Uterine Milk 



The existence of a nutritive juice in the uterus of Ruminants 

 during pregnancy has been recognised since the days of Harvey. 

 He spoke of an albuminous fluid, which might be squeezed out 

 from the cotyledons of the placenta, as a source of nutriment 

 for the foetus. As to its origin, he says in one of his Letters : 

 " It might be transported by the uterine arteries and distilled 

 into the uterus." The fluid was first called uterine milk by 

 Needham in 1667. Haller described it as a secretion of the 

 utricular glands, and this view was supported by Bischoff, 

 Sharpey, and others, who considered it the immediate store of 



1 For the above account of the development and structure of the sheep's 

 placenta, we are largely indebted to the important memoir of Assheton. 

 Differing in many respects from previous descriptions, it alone brings forward 

 evidence that the Ungulate placenta may be " secondarily simplified " in 

 Hubrecht's sense (see Quar. Jour. Micr. Sci., 1908). 



2 Ledermann, " Ueber den Bau der Cotyledonen im Uterus von Bos," &c. 

 Inaug.-Diss., Berlin, 1903. 



