mi: ORGANS OF mi: r 





duct is added iu tin- murse of another -lay. Al-o in the case of 

 hiiiiian embryos -1 nun. long His demonstrate 1 ti. i there if* 



only a single hepatic duct, ami that some time at'teru ards a ft 

 appears ( tig. 1 il.'J /./'.</) 



In the further course of development both the impure 1 and the 

 paired hepatic fun da merit s an- metamorphosed (put*- rapidly into 

 a tuluilar gland \\itli numerous branches; this acquires a special 

 chaiacter. differing from that of simple tubular gland-. >\\ing to 

 the tact that the tubes early become joined together to form a tine 

 network, .since the primitive hepatic tubes send out numerous 

 lateral buds, which in some Vn tebrates 

 (Amphibia, Selachii) are from the be- 

 ginning hollow, in others (Birds. Mam- 

 mals. Man) solid. Imbedded in the 

 embryonic connective substance of the 

 vent ral mosogastrium, they grow out in 

 the former case into hollow tub 

 the latter into solid cylinders. Th- 

 in turn are soon covered with corre- 

 sponding lateral processes, and so on. 

 Ilia-much a> these grow toward die 

 another, and where t hey meet(fig. lS7lc) 

 fuse, there arises a close network <>t 

 hollow glandular canals or solid hepatic 

 cylinders in the common coniie. 

 tiu.- matrix. 



Simultaneously with the epithelial 

 network there is formed in it>me-h.-, 

 a network of blood-vessels (g). From 

 the vena omphaloniosenterica, which, 



as previously stated, is embraced by the two Inpatic tub 

 L'IOW out numerous shoots, and these by forming lateral ln-ai. 

 unite with one anothtr in a mannei- corresponding to that of t!ie 

 hepatic cylind 



The liver of the Chick i> found t< lw in this condition on the sixth 

 day. It has become e\vn imw a rather volumiiuuis <r^an. and is 

 composed, as in the case of Mammals and Man, of two equally 

 large lob->. each of which has ari-en from one of the two primitive 

 htpatic ducts by budding. The t\\ lies produce >n the vt-ntral 

 mesi'iitery two ridges, one of which projects into the left body-cavity 

 and one into the riirht (fig. 184). 



Fig. 186. -Diagrammatic view of th 

 alimentary canal of a Chick on 

 the fourth day, after G- 



The heavy line indicates the inner 

 germ-layer, the shaded portion 

 MM t,.i;n, I..,.: it the splanchnic 

 u of the nieaoblaat lg t 

 Lung ; St, stomach ; p, pancreas ; 

 I, liver. 



