Embryonic Development in Man. 395 



differentiated into a compacta and a spongiosa. How far distant 

 from the ovum these characters have already been established we 

 cannot say, since only the ovum and its next neighborhood have 

 been sectioned and examined. 



Jung, who, in his ovum, likwise found a distinct differentiation 

 into a compacta and spongiosa quoted Hitchman and Adler's observa- 

 tion of the uterine mucosa before and during menstruation. These 

 authors, even in the absence of gestation, found in the premenstrual 

 period a temporary formation of a compacta and spongiosa. We 

 have ourselves studied the menstrual changes on several specimens 

 obtained per operationem and at once properly fixed, and we have 

 previously (The Pathology of Tubal Pregnancy), summarily de- 

 scribed them as follows : "'The capillaries of the inter-tubular con- 

 nective tissue are enormously dilated and densely filled with red 

 blood corpuscles. Many of the latter are also found free, outside 

 of the capillaries, between the connective tissue cells of the inter- 

 glandular spaces. The whole mucosa is edematous and the connec- 

 tive tissue cells are pushed apart by the edematous and hemorrhagic 

 infiltration. Some of the connective tissue cells, which in the inter- 

 menstrual periods are normally all of the type of small lymphoid 

 cells, are enlarged, oval or fusiform. They assume a type found 

 in certain forms of endometritis interstitialis and approach the type 

 of decidual cells. It may really be said that the uterine mucosa 

 in menstruation shows to a very slight extent the beginning stage of 

 a decidua. Most of the surface epithelia of the mucosa are pre- 

 served; only a few are missing here and there. Changes similar 

 to those described as characteristic for the menstruating uterine 

 mucosa I have twice observed in the tubal mucosa during menstrua- 

 tion." 



The decidua spongiosa is considerably thicker than the compacta 

 (Fig. 26). In the former we find irregular gland spaces, much 

 crowded, and separated from each other by small bridges of tissue. 

 The proliferative energy of the glandular epithelium is shown by 

 the fact that it is found inside of the gland space proper, in the 

 shape of projecting papillary ridges, septa and digit-like processes. 

 All of these masses of epithelia are lined up on a slender basis of con- 



