FCETAL NUTRITION: THE PLACENTA 435 



maternal part of the biui- appeai'H to be digested and absorbed by the 

 tropholilast. The greater activit}- of the fcptal ectoderm in the deer 

 is also shown by the destruction of the epithelium over the whole 

 surface of the uterus (StrahP). 



-■ai? 



ri&r. 









3 



o © © e ® o© 







Fig. 118. — Histology of the placenta in the cow and sheep. (From Jenkinson, 

 Vi'rti-hrate Emhri/ology, Oxfoi'd, at the Clarendon Pi'ess.) 



1. Fcetal and matei'nal tissues in a cotyledon, tr, Tiophoblast of a ^■illus ; the 



cells are absorbing fat (black). In the trophoblast are binucleate cells. 

 Behind it are the connective tissue and blood-ves.sels of the allantois. 

 ep. Uterine epithelium lining a crypt. Fat secretion is going on, the ends 

 of the celts with fat globules being pinched ott' and thrown into the crypt's 

 lumen. Below the epithelium are maternal capillaries and connective tissue. 



2. Columnar trophoblast cells form between the bases of the cotyledonaiy villi. 



The cells contain ingested matter (corpuscles, nuclear, and cell debris). 



3. Ingestion of extravasated maternal coi'puscles by the trophoblast in the 



sheep. The cells contain pigment besidei5 cor]juscles. 



4. Deposition of pigment derived from h;emoglobin of ingested coipuscles in 



trophoblast cells of cow. The pigment granules (black) are deposited in 

 irregulai- masses. 



In addition to Wood, the uterine milk contains fat in large 

 quantities. Befoie pregnane}' it may Ije demonstrated in tlie sub- 

 epithelial leucocytes which later migrate to the suiface. Fat glo):)ulos 

 are also contained in large amount in the epithelial cells (jf the 



' Strahl, " Ueber die Semiplacenta multiplex von Cerrt'x eliiphux 

 llej'te, H. xciii., 1906. 



A nut. 



