440 THE PHYSIOLOGY OF REPRODUCTION 



of the embryotrophe — in the trophoblast. Many, if not all, of the 

 cellular elements are partially degenerated before absorption. The 

 appearances suggest an enzyme action on the part of the ti-ophoblastj 

 and perhaps also the leucocytes, but no proteolytic or hpolytic enzyme 

 is contained in glycerin extracts of the maternal or foetal part of the 

 cotyledon. 



After their absorption, the disintegration of the cellular constit- 

 uents is completed in the trophoblast, and they are no longer 

 recognisable as individual elements. Their products are transmitted 

 to the fcetal vessels, though they may first be elaborated in the 

 trophoblast into a form or forms suitable for the use of the embryo 

 in the development of its various organs. 



Lemuroidea. — Many of the lemurs have a simple avillous diffuse 

 placenta, as Turner ^ first pointed out in specimens from Madagascar. 

 Hubrecht has investigated two others found in the East Indies — 

 Tarsius^ and Nycticebus? The latter has also a diffuse placenta. 

 Villi develop over the whole of the chorion, and fit into vascular 

 crypts in the uterine mucosa from which they are easily retracted at 

 birth.. The epithelium of the crypts persists as in the cow, and the 

 " osmotic interchange takes place through two cell-layers of different 

 origin, and of different physiological significance (phylogeneticaUy). 

 Tarsius approaches more closely to the Insectivora and Primates. 

 The trophoblast proliferates and penetrates into the mucosa, and 

 maternal blood circulates in its spaces. The mesoblast grows 

 profusely, and forms with the trophoblast a true chorion in Hubrecht's 

 , restricted sense. The placenta is discoid. In Galago agisymhamis, 

 Strahl * has shown that a layer of secretion lies between the uterus 

 and the ovum from the beginning of pregnancy. It is absorbed by 

 the ectoderm, the cells of which are vesiculated over the gland orifices. 

 Many blood extravasations occur in the connective tissue of the 

 mucosa, and the red blood corpuscles undergo changes as in the sheep, 

 the glandular cells and embryotrophe containing granules which give 

 an iron reaction. At the extremity of each chorionic villus is a slight 

 pit the cells suiTOunding which contain a granular greenish substance 

 derived presumably from haemoglobin. Turner ^ had previously noted 

 in lemurs the intense brown staining of the glands from effused 

 blood. 



1 Turner, "On the Placentation of the Lemurs,'' Phil. Trans. Roy. Soc, 

 London, vol. clxvi., 1876. 



2 Hubrecht, " Ueber die Bntwicklung des Placenta von Tarsius, etc.," Internai. 

 Congr. of Zool., Cambridge, 1898. 



^ Hubrecht, " Spolia Nemoris," Quar. Jour. Mia: Science, vol. xxxvi., 1895. 



* Strahl, "Die Verarbeitung von Blutextravasaten durch Uterindrusen," 

 Anat. Anzeic/., vol. xvi., 1899. 



^ Turner, "The Placentation of Lemurs," ./onr. of Anat. mid.Phi/i., vol. xii., 

 1878. 



