592 GENERATION AND DEVELOPMENT. 



that, at the villi of the placental tufts, where the foetal and 

 maternal portions of the placenta are brought into close rela- 

 tion with each other, the blood in the vessels of the mother is 

 separated from that in the vessels of the fetus by the inter- 

 vention of two distinct sets of nucleated cells (Fig. 229). One 

 of these (6) belongs to the maternal portion of the placenta, is 

 placed between the membrane of the villus and that of the 

 vascular system of the mother, and is probably designed to 

 separate from the blood of the parent the materials destined 

 for the blood of the foetus ; the other (/) belongs to the foetal 

 portion of the placenta, is situated between the membrane of 

 the villus and the loop of vessels contained within, and prob- 

 ably serves for the absorption of the material secreted by the 

 other sets of cells, and for its conveyance into the bloodvessels 

 of the foetus. Between the two sets of cells with their invest- 

 ing membrane there exists a space (cT), into which it is proba- 

 ble that the materials secreted by 

 FIG. 229. -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 ves- 

 sels. 



Not only, however, is there a 

 passage of materials from the 

 blood of the mother into that of 

 the foetus, but there can be no 



Extremity of a placental villus. a, doubt of the existence of a mu- 



lining membrane of the vascular tual interchange of materials be- 



system of the mother; ft, cells im- , ji r i j r .1 .<? j? j. j 



mediately lininga; d, space between tween the Wood both of fotUS and 



the maternal and fetal portions of of parent, the latter supplying the 

 the villus ; e, internal membrane of former with nutriment, and in turn 

 the villus, or external membrane of abstracting from it materials which 



the chorion ; /, internal cells of the require to be removed. Dr. Alex- 

 villus. or cells of the chorion ; a, loop j -rr > 



of umbilical vessel (after Goodsir). andei \ Harvey s experiments were 



very decisive on this point, ihe 

 view has also received abundant 



support of late from Mr. Hutchinson's important observations 

 on the communication 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 of strychnia into the 

 abdominal cavity of one foetus, and into the thoracic cavity of 

 another, and then replaced all the parts, every precaution 

 being taken to prevent escape of the poison. In less than 



