FCETAL NUTRITION: THE PLACENTA 



447 



network are penetrated by the vessels of the villi. In this way, 

 according to Duval, the labyrinth is formed. In it the maternal and 

 the fcetal blood are separated by the endothelium of the uterine 

 capillaries, a cellular layer (considered foetal by Duval and maternal 

 by Heinricius) which later disappears, the syncytium, mesoblast, and 

 foetal capillary walls. 



At places, however, the villi come directly in contact with 

 maternal blood, especially at the "green border" of the placenta. 



Fis. 1-25. — ^Th© labyrinth and the green border of the placenta of the dog at 

 the fortieth day of pregnancy. To the right are two lobules of the 

 angioplasmode which have reached the stage of complexity of the 

 labyrinthine lamellse : to the left is the green border, the cavities of 

 which, normally filled with blood, are indicated by a cross. (From Duval's 

 " Le Placenta des Carnassiers," Joiir. de VAnat. et de la Phys., 189.3.) 



1, 2, and 3, Basal lamellas of the green border ; 4, basal lamella of lobule 



of labyrinth. 



which forms a characteristic appearance in some of the Carnivora. 

 In all the members of the order, larger or smaller maternal 

 haemorrhages occur at an early period after the attachment of the 

 blastodermic vesicle. The effusions vary in size and position. In 

 the dog they occur regularly along the margins of the placental zone, 

 and form the lordnire verte; in addition smaller haemorrhages take 

 place into the substance of the placenta, and form the "green 

 pockets," which may be isolated or joined to the green border by 

 bridges (Fig. 125). In the cat the haBmorrhages occur in irregular 

 positions and do not assume the green colour typical of the dog. 

 Indications of a green border are present in the earlier stages, but 



