274 Royal Society. 



the secreting cells, although some remain isolated, for the most 

 part coalesce to form tubes, having a succession of dilatations 

 and constrictions, and finally uniting and opening into the intes- 

 tine. In Insects, the usual arrangement is that of long curved fila- 

 mentary tubes, which wind about the intestine ; these, in the meat 

 fly, are sacculated throughout the greater part of their course, till 

 they arrive quite close to the pylorus, where they open ; near their 

 origin they appear to consist of separate vesicles, which become 

 gradually fused together, but occasionally they are seen quite sepa- 

 rate. The basement membrane of the tubes is strongly marked, 

 and encloses a large quantity of granular matter of a yellowish tinge, 

 with secreting cells ; another portion of the liver consists of sepa- 

 rate cells lying in a granular blastema, which cells, in a later stage 

 of development, are seen to be included in vesicles or short tubes 

 of homogeneous membrane, often coalescing and exhibiting a more 

 or less manifestly plexiform arrangement ; this portion of the 

 liver is regarded by Mr. Newport as really adipose tissue. The 

 author has termed it the parenchymatous portion of the liver, on 

 account of its general appearance and mode of development, though 

 he has not been able to determine whether the tubes always origi- 

 nate from it. Among the Arachnida, the follicular type of arrange- 

 ment prevails; and the same is the case with the Crustacea, the folli- 

 cles in these last being distinctly visible to the naked eye. In Mol- 

 lusca also, we find the follicular arrangement universally to obtain ; 

 yet in certain cases the limiting membrane of the follicles cannot be 

 shown to exist, and the author therefore thinks that its importance 

 is probably not great, but that it serves chiefly to fulfil the me- 

 chanical function which its synonym u basement" indicates. The 

 quantity of retained secretion in the liver of molluscs seems clearly 

 to imply that the bile in them is not an excrementitious fluid ; it is 

 used slowly on account of the imperfect character of the respira- 

 tion. 



In passing from the Invertebrata to the Vertebrate division of the 

 animal kingdom, and beginning with the class of Fishes, a great 

 change is immediately manifest in the form and character of the 

 biliary organ ; it is now a gland of solid texture, to which the term 

 parenchymal is justly applied. Two portions may be distinguished 

 in it, namely, the secreting parenchyma, consisting of delicate cells, 

 or very often of nuclei, granular and elaborated matters in great 

 part, and the excreting ducts, which, though completely obscured 

 by the surrounding bulky parenchyma, may yet be satisfactorily de- 

 monstrated, and traced often to their terminal extremities in the 

 following manner. If a branch of the hepatic duct be taken up in 

 the forceps, it may be dissected out without much difficulty from 

 the surrounding substance, which is very soft and yields readily to 

 gentle manipulation ; when a trunk is in this way removed and 

 placed under the microscope, a multitude of minute ramifications 

 are seen adhering to it ; among these not a few may be discovered, 

 which do not appear to have suffered injury ; some are occasionally 

 seen terminating by distinctly closed extremities ; more usually the 



