AND FUNCTION OF THE LIVER. 
11 
is replaced by granulous ; pigment granules at the same time are deposited upon and 
in the vesicular nuclei, and thus those yellow and brown-coloured masses are formed 
which are so apparent in the liver of the adult animal. The gall-bladder for some 
time contains only a transparent fluid, which is coagulated in a marked manner by 
nitric acid, and is therefore probably only a solution of albumen ; after a time the 
fluid in this receptacle has a biliary tinge, and then is not coagulated by the action 
of nitric acid. This was at least the case in two instances, though in another at a 
still later period the acid produced a precipitate which however may have been only 
mucus. 
The general conclusions respecting the development of the liver in the Frog may 
be stated as follows : — 
(1.) That a portion of the common formative yolk substance contained in the 
abdomen is set apart for the development of the liver. 
(2.) That this occurs at about the same time when the intestine begins to be formed, 
so that the liver is not in any way derived from the intestine. 
(3.) That the first rudiment of the efierent apparatus is the gall-bladder, and that 
the ducts are subsequently formed. 
(4.) That a cystic duct is first formed, conneeting the gall-bladder with the intes- 
tine, and that hepatic ducts are subsequently developed. 
(5.) That these ducts are at first solid tracts, and as well as the gall-bladder 
primarily consist of similar formative substance to that which composes the liver. 
I may add here that I have seen very distinctly the ciliary motion on the outer 
tegumentary surface of tadpoles as described by Dr. Gairdner; my observa- 
tions were made several months before I had the pleasure of reading his description 
of it. 
I may remark that I have obtained some very satisfactory views of the minute 
biliary ducts in the liver of a Rook (Corvus) by stripping out branches of the portal 
vein and washing away the parenchyma. The ducts were then seen here and there 
lying upon the homogeneous membrane of the vein-branches. Their condition was 
essentially and closely similar to that described in my former paper. 
Development in Birds. 
Since the publication of the account I gave in my previous paper of the develop- 
ment of the liver in the Chick, I have twice repeated my observations, and have 
found the views I advanced in the main correct. I think, however, it may be worth 
while to review some stages of the progress which it is important to investigate 
thoroughly. 
The formation of the intestine takes place by the constriction of the central trans- 
parent portion of the germinal membrane; this seems to me to be a homogeneous 
membranous expanse, not composed of cells, and covered only with oil-drops, while 
the rest of the germinal membrane with which it is continuous is covered by adhe- 
c 2 
