1906.1 PLACENTA IN UXGULATES. '5 



and digested ; as a result pigment appears in the cells, while iron 

 can be demonstrated in the fluid in the uterine cavity. 



A recent examination of a fairly complete series of stages ot 

 the placentation of the Cow and Sheep has enabled me to confirm 

 Kolstei's valuable observations in all essential particulars : tue 

 secretion of cells in the uterine glands, the secretion and absorp- 

 tion of fat in the cotyledons (1 have never succeeded in finding 

 fat in the extra- cotyledonary uterus, though it is abundant in 

 the overlying trophoblast), the disintegration of large masses of 

 maternal tissue, the extravasation of red corpuscles and then- in- 

 gestion by the trophoblast with consequent formation ot pigment, 

 the emigration of leucocytes through the uterine epitlielium,— 

 certainly all occur in the manner described by this author. At 

 the same time there are one or two small points on which I am 

 unable to agree with him, such as the disappearance of the epi- 

 thelial cilia and the mode of formation of the accessory cotyledons ; 

 and others where his description or figures are deficient— the 

 histology of the trophoblast, for example. Further, the pigment 

 was not examined spectroscopically by Kolster, and neither 

 Kolster nor Bonnet has paid the slightest attention to a highly 

 important substance, the glycogen of the placenta. Lastly, I have 

 made one or two interesting observations on the anatomy ot the 

 "diverticulum allantoidis" and on the origin of the allantoic 

 bodies or hippomanes. _ _ 



My material includes pregnant uteri containing embryos ot from 

 4 cm to 60 cm. in length in the case of the Cow, from 14 cm 

 loner to full time in the case of the Sheep, of the after-birth foetal 

 membranes of the Cow, and non-pregnant uteri both virgin and 

 post-partum. 



The preservative fluids used were aceto-corrosive, picro-corro- 

 sive, Flemming, and 'JO per cent, alcohol. It may be pointed out 

 that for the proper preservation of the maternal epithelial tissues 

 it is essential that the uterus should be pinned out, with the 

 overlying trophoblast and allantois, before it is placed m the 

 fixative. 



1. The Formcdion of Accessory Cotyledons. 



It is well known that in the Cow and Sheep the maternal 

 cotyledons are formed in certain definite areas which can be dis- 

 tinguished in the virgin uterus (even of the unborn uterus) as 

 rounded prominences of the mucosa— the cotyledonary caruncles. 

 These caruncles consist of a dense mass of vasifactive sub-epi- 

 thelial connective tissue, and are covered by a columnar epithelium 

 continuous with that which lines the rest of the uterine ca^ ity. 

 They contain no glands. 



After impregnation has taken place the caruncles are converted— 

 upon the atta,chment of the blastocyst to the uterine wall— into 

 the maternal cotyledons, becoming pitted by the crypts m which 

 the fcetal villi lie. The number of cotyledons thus formed is 

 therefore predetermined and definite ; but in addition to these 



