758 GENERATION AND DEVELOPMENT. 



parent the materials destined for the blood of the foetus ; 

 the other (f) belongs to the foetal portion of the placenta, 

 is situated between the membrane of the villus and 

 the loop of vessels contained within, and probably serves 

 for the absorption of the material secreted by the other 

 sets of cells, and for its conveyance into the blood-vessels 

 of the foetus. Between the two sets of cells with 

 their investing membrane there exists a space (dj, 

 Fig. 223*. into which it is probable that the 



materials secreted by the one set of 

 cells of the villus are poured, in 

 order that they may be absorbed 

 by the other set, and thus conveyed 

 into the foetal vessels. 



Not only, however, is there a pas- 

 sage of materials from the blood of 

 the mother into that of the foetus, but there can be no doubt 

 of the existence of a mutual interchange of materials between 

 the blood both of foetus and of parent, the latter supplying 

 the former with nutriment, and in turn abstracting from it 

 materials which require to be removed. Dr. Alexander 

 Harvey's experiments were very decisive on this point. 

 The view has also received abundant support of late from 

 Mr. Hutchinson's important observations on the communi- 

 cation of syphilis from the father to the mother, through 

 the instrumentality of the foetus ; and still more from 

 Mr. Savory's experimental researches, which prove quite 

 clearly that the female parent may be directly inoculated 

 through the foetus. Having opened the abdomen and 

 uterus of a pregnant bitch, Mr. Savory injected a solution 



Fig. 223. Extremity of a placental villus. a, lining membrane 

 of the vascular system of the mother ; b, Cells immediately lining a ; 

 d, space between the maternal and foetal portions of the villus; e, 

 internal membrane of the villus, or external membrane of the chorion 

 /, internal cells of the villus, or cells of the chorion ; g, loop of umbilical 

 vessels (after Goodsir). 



