TIN: Hi.TM. \M:MI:|{.\M-:S or MAMMALS. 235 



corresponding thickenings of the uterine mucous n th-- 



placenta- uteiinte (C 11 ), though nl\ in a loose manner, M> tliat a little 

 pulling is sullident to produce a ,-eparat ion. and to draw the dun-ionic 

 villi out of the depressions \\liidi serve for their reception, as one 

 draws the hand out of a glove. In fact, in the preparat ion which 

 MTVefl M tlie 1 aftifl of our liguiv i:>fa the cotyledons of ollspring and 

 mother (t '- 'and C 1 ) are separated from eadi other, sine.- the uterus 

 (U) has been opened by means of an incision and drawn hack from 

 the chorion (Ch) for a little distune -. 



l-'i^ure l,'J5h shows a single cotyledon of figure 135a pomewhat 

 larger than the natural size. The wall of the uterus (u) is drawn 

 hack a little from the chorion (Ch). As a result of this, the maternal 

 (C 1 ) and foetal parts (C 2 ) of the cotyledon are partially sepai 

 from each other. On the placenta uterina (C 1 ) one perceives many 

 small pit-, on the placenta fcetalis (C 2 ) the closely packed dendritically 

 branching chorionic villi, which have been withdrawn from the 

 nits. 



As the diagrammatic section figure 136 teaches, the fcetal and 

 maternal tissues abut immediately on each other. The villi are 

 covered with flattened cells, and the depressions of the mucous 

 membrane are lined with cylindrical cells ; the latter develop within 

 them granules of fat and albumen; they disintegrate in part, and 

 thereby contribute to the formation of a milky fluid, the so-called 

 uterine milk, which can be pressed out of the placenta uterina and 

 serves for the nutrition of the foetus. It is to be noticed also that 

 in the Ruminants the uterine glands have openings on the mucous 

 membrane only between the cotyledons. 



In all other Mammals that are provided with a placenta the 

 intrrgnwth of the fcetal and maternal tissue is still more intimate. 

 At the same time there is formed in this way such a close union, 

 that a stpartUion <;f the chorion without i/ijtir// to the mucous mem? 

 <>/ the uterus is now no longer possible. At f>irt/t therefore a more or 

 less considerable superficial layer of the mucous m> m Irnne of the v' 



't off with the foetal placenta. The part that is cast oft* is called 

 the caducous membrane, or the dec! 'tun. 



In accordance with Hr.\i.K\'s propo>al, all Mammals in which, in 

 consequence of the special growth of the placenta, such a membrane 

 is formed are now grouped together afl Mammalia dtciduata, or 

 briefly Deciduata, in contradistinction to the remaining Mammals 

 the InoVjciduata, the formation of whose placenta- has jiu>t been 

 discussed. 



