410 THE RABBIT. 



the proportions are not very unlike tliose of the adult. The 

 glottis, LT, at this stage is a longitudinal slit-like opening in the 

 ventral wall of the oesophagus ; it is overhung by the epiglottis 

 (c/. Fig. 150, le), a fold at the back of the pharynx, marked ofiE" 

 -from the tongue by a well-marked transverse groove. The glottis 

 leads into a dilated laryngeal chamber (Fig. 151), which is 

 continued down the neck as the trachea, lr. The thyroid, CT, 

 cricoid, and tracheal cartilaginous rings are already present, and 

 have the same relations as in the adult. 



5. The Liver. 



The liver of the rabbit, like so many other important organs, 

 commences on the tenth day, arising as a diverticulum from the 

 ventral surface of the mesenteron, about the junction of the 

 stomach and duodenum. This diverticulum, which becomes the 

 left bile duct of the adult, is directed ventralwards, and its blind 

 end is in close relation with a thickened mass of condensed 

 mesoblast which forms part of the ventral body-wall of the 

 embryo, behind the heart, and in front of the yolk-stalk. 



On the eleventh day, the right bile duct arises as an out- 

 growth from the left duct, close to its opening into the 

 duodenum. From the lining epithelium of both right and 

 left ducts, solid rods of hypoblast cells, the hepatic cylinders, 

 grow out into the mass of condensed mesoblast around them. 

 The hepatic cylinders branch and anastomose freely, forming a 

 reticulum, the meshes of which are occupied by the connective 

 tissue, in which blood-vessels early appear in large numbers. 



By a series of further changes, which have not yet been 

 accurately determined in the rabbit, the adult liver is formed. 

 The cells of the reticulum become the hepatic cells, which are 

 thus of hypoblastic origin ; while some at least of the cylindrical 

 rods become hollow, and form the bile passages, which com- 

 municate directly or indirectly with the bile ducts (cf. Fig. 

 150, w). 



The gall bladder arises on the eleventh day, as a diverticulum 

 form the right bile duct. 



The relations of the blood-vessels to the liver are much the 

 same as in the chick, and will be described more fully in the 

 section dealing with the development of the vascular system. 

 It may be noticed here that in its early stages the liver has, as 



