74 DR. J. W. JEXKINSOX OX THE [Feb. 6, 



valuable food for the developing ffetus ; not only can the troplio- 

 blast be shown to be absorl)ing fat even while the blastocyst is 

 still floating fi-eely in the lumen of the uterus, but the cells of 

 this fojtal membrane are also phagocytic and actively ingest the 

 solid particles of the uterine milk. This food-material is of 

 maternal origin ; fat is secreted by the uterine epithelium and 

 glands, the i"ed blood- corpuscles are extra va sated from superficial 

 Ciipillaries, while the leucocytes emigrate through the epithelial 

 cells, the Stiibchen are formed by the cells of the maternal epi- 

 thelium, and the degenerating celluhu- masses result from the 

 extensive disintegrat-on of epithelial and subepithelial tissue. 



More recently the studies of Kolster on the placentation of the 

 Horse, Cow, Sheep, Pig, Roe-deer, and Red-deer have thrown 

 additional liglit on the mode of manufacture of this valuable food- 

 supply. 



This author, while fully corroborating Bonnet's account of the 

 secretion of fat in the extra-cotyle denary uterine epithelium 

 and its glands, and of the copious emigration of leucocytes thi-ough 

 the epithelium during the greater part of gestation, has given a 

 more detailed description of the histological nature of these and 

 other processes. In fat-secretion the outer end of the cell with 

 the fat-globides it contains is j)rotrude(l into the lumen of the 

 uterus or of the gland, pinched ofl", and ejected ; exactly the same 

 process, which evidently resembles very closely the formation of 

 milk in a mammary gland, occuis in the secretion of fat in the 

 crypts of the maternal cot^dedons. The fat so secreted is quickly 

 absorbed by the ti-ophob^ast. 



Another very interesting phenomenon described by Kolster 

 is the production by the glands of a " cellular secretion," in 

 addition to the thin coagulable liquid substance usually found 

 in them ; here and there small tracts of the epithelial wall 

 become invaginated into the gland-lumen, and being cut off 

 degenerate and are ejecteel by the mouths and added to the 

 uterine milk. The epithelial cells so cast out are often accom- 

 panied by connective-tissue coipuscles and leucocytes. Bonnet 

 has recently demonstiated a similar "cell-secretion" in the 

 uterine glands of tlie bitch. These ejected gland-cells form 

 a very impoitant though not an only* source for the cellular 

 constituents of the milk. Considerable masses of disinte- 

 grating maternal tissue are added to the whole, ss well as 

 quantities of red corpuscles. All this material is ingested by the 

 phagocyctic trophoblast ; the foetus is thus able to obtain a large 

 amount of proteid food and — from the red corpuscles — the 

 essential iron as well. The result of the intra-trophoblastic 

 digestion of the hjemoglobin is the formation of pigment-masses 

 in the cells of this layer ; these masses will sometimes give an iron 

 reaction, but usually not. The pigment was not furthei' investi- 

 gated by Kolster. A very similar pigment is formed by the 

 exti-avasation of blood from subepithelial Ciipillaries at the time 

 of heat, the blood-corpust-les being taken up by wandering cells 



