146 



somewhat irregular. Further details are given of the condition of 

 the ultimate and penultimate ducts in the several vertebrate classes. 



In the class of Fishes, the minute ducts most commonly appear as 

 solid cylinders of soft granulous substance, in which scarce anything 

 but some oily molecules are to be discerned ; but not very unfre- 

 quently two other conditions are observed, which seem to illustrate 

 very vrell the active character of the function of the duct. In the 

 first the granulous m^atter exists in much smaller quantity, and the 

 nuclei imbedded in it are consequently seen m-uch more distinctly ; 

 their presence is thus unequivocally determined ; it is shown that 

 there is no real difference between the ducts of the fish's and those 

 of the mammalian liver, only that the granulous matter is usually 

 accumulated in the former more abundantly than in the latter. The 

 presence of free nuclei in granulous matter indicates an active change 

 to be proceeding in the part. In the second condition sometimes 

 observed the granulous matter lies imbedded in it, a vaiying number 

 of pellucid vesicles of great delicacy, but quite distinct ; these testify 

 that a process of active growth takes place in the minute ducts, and 

 show, the author thinks conclusiveh^ that the seminute ducts are 

 not mere efferent canals. 



Su^ar was detected on tWo or three occasions in the livers of 

 fishes ; it seems to be absent when the organ is extremicly fatty. 



In the minute hepatic ducts of reptiles, the condition of the epi- 

 thelium is very similar to that in fishes; the nuclei sometimes ap- 

 pearing with great distinctness, sometimes being obscured by much 

 granulous matter, sometimes developing themselves into pellucid 

 vesicles. The livers of frogs and toads almost constantly contain 

 dark yellow^ masses which w^ere formerly regarded by the author as 

 biliary concretions, but are now considered to be only pigmentary 

 deposits ; they coexist sometimes vrith much diffused black matter. 



The ultimate ducts have been traced recently very satisfactorily 

 in Birds, Mammalia and Man, and the description given of them in 

 the paper accords with the author's former account. 



The development of the liver and its apparatus of ducts has been 

 traced out in fishes and reptiles, and the following results obtained 

 in both classes. 



(1.) The liver (i. e. the parenchyma of the organ) is formed as an 

 independent mass, and does not proceed as an effect fi-om the in- 

 testine. 



(2.) The gall-bladder is developed separately as a transparent 

 ' vesicle, containing a clear fluid. 



(.3.) The gall-bladder elongates itself at one end, tends towards 

 the intestine, and at last opens into it, while from one part of its 

 extent hepatic ducts are developed ; in the Frog the hepatic ducts 

 seem, however, to be formed at the same time as the gall-bladder, 

 and to be developed pari passu along with it= The cystic duct is 

 lined by ciliary epithelium which plays very actively. 



The examination of the process of development in the chick has 

 confirmed, so far as it was carried, the account given in the former 

 paper. 



