346 THE DEVELOPMENT OF THE CHICK 
to the left side of the body-cavity (Fig. 188), and which is 
exaggerated by the rapid growth of the dorsal pancreas (Choron- 
schitzky). The spleen is thus genetically related to the wall of 
the great omentum, and hes outside the cavity of the latter. 
The cells of the spleen are proliferated from a peritoneal thicken- 
ing, Which may be compared in this respect to the germinal 
epithelium. It is recognizable at ninety-six hours, and the mass 
formed by its proliferation grows rapidly, forming a very consid- 
erable projection into the left side of the body-cavity above 
the stomach, at six days (cf. Fig. 197). 
Bomin 
~~--~Bomay 
Fig. 196. — The same model from the left side. (After Broman.) 
Hrpesin., Hiatus recessus pneumato-entericus sinister. 1. Br., 
Left bronchus. Pr’v., Proventriculus. Rhesin., Recessus hepato- 
entericus sinister. Rpesin., Right pneumato-enteric recess. Other 
abbreviations as in Fig. 195. 
According to Choronschitzky, the peritoneal cells invade the 
neighboring mesenchyme, and, spreading through it, form an ill- 
defined denser area, the fundamental tissue of which is therefore 
mesenchymal. The meshes of the latter are in immediate con- 
tinuity with the vena lienalis, but the vascular endothelium is 
