EMBRYO WITH TWENTY -EIGHT SEGMENTS. 



209 



mal canal spring two small pouches or diverticula, the anlages of the liver. The 

 left diverticulum is well shown in the figure; the right diverticulum appears a 

 few sections farther on. It is especially important to note that the entodermal 

 epithelium of the hepatic diverticulum comes into immediate contact with the endo- . 

 thelium of the blood spaces. During the later development this relation is preserved, 

 and there is a complicated intercrescence of the entodermal cells constituting the 

 liver and of the vascular endothelium.* The intercrescence leads to the forma- 



Som. 



Spl. 



Om.S. 



Om. D. 





FIG. 158. SECTION OF CHICK EMBRYO WITH ABOUT TWENTY-EIGHT SEGMKNTS. TRANSVERSE SERIES 92, 



SECTION 179. 



Am, Amnion. Ao, Aorta, card, Cardinal vein. Cho, Chorion. Cos, Coelom. Ent, Entoderm. In, Intestine. 

 msth, Mesothelium. My, Muscle plate, nch, Notochord. Om.D, Right omphalo-mesaraic vein. Om.S, 

 Left omphalo-mesaraic vein. Som, Somatopleure. Sp.c, Spinal cord. Spl, Splanchnopleure. X 50 diams. 



tion of the sinusoids, which are highly characteristic of the liver and which give 

 rise to the so-called capillaries of the hepatic lobules of the adult liver. These 

 "capillaries" are, however, 'always true sinusoids, and morphological!;*' not capil- 

 laries at all. Owing to the junction of the veins and liver, a portion of the body 

 cavity, Cce f , at the side of the pharynx is shut off from direct Connection with 

 the pericardial cavity. The ridge of tissue dividing the two cavitjes from one an- 

 other is the tjeptum transvcrsum. 11" the ser ns be followed through tail- 



* A few sections anterior to this the beginning of the inten i 



