18 
DK. C. H. JONES ON THE STRUCTURE, DEVELOPxMENT 
and of fish there is scarce any trace of bile to be discerned, while in the follicular 
liver of IMollusca the dark biliary matter very greatly preponderates over the oily ; 
sometimes, as has been mentioned, we see different parts of the lobules the seat of oil 
and bile respectively; and this is most usually the case, though there is no doubt that 
the two products may coexist in the same cell*. 
The exact relation which the smaller and terminal ducts bear to the parenchyma 
is the present “vexata queestio,” and any observations that tend to elucidate this 
matter, and render it more easily determined, are worth our attention. I have made 
many examinations since the publication of my last paper relative to this point, and 
have been by them decidedly confirmed in the views there expressed. I stated that 1 
believed the ducts did not ramify extensively, did not extend far beyond the “ spaces,” 
and that many fissures seemed quite destitute of them. This is, I think, generally 
the case, but in some instances the ducts seem to extend farther than otheis ; with 
regard, however, to the main point, that the cells are a parenchyma, and not an epi- 
thelium, I entertain no doubt whatever. In many, if not in all London dogs, and in 
some rabbits, there is found a peculiar condition of the epithelium of the whole 
excretorv apparatus of the liver, which renders it comparatively easy to trace and 
follow the ducts to their terminations. If thin sections be made of such livers, the 
ducts are seen as opake tubes or tracts, appearing whitish by direct light, which 
come up from below at the “ spaces,” where three lobules adjoin, divide irregularly, 
and run for a varying distance along the fissures. These tubes run often a long 
distance without branching ; they are most often single, one only traversing each 
portal canal or fissure, and what is especially remarkable, not maintaining any close 
relation to the wall of parenchyma, between which and them a distinct interval is 
often to be seen. 
Their mode of termination varies; sometimes they break up into a few delicate 
branches, which may give the appearance of a plexus ; sometimes they terminate by 
apparently losing themselves, that is to say, they gradually cease, their structure 
being indiscernible beyond a certain point, or breaking up into a mere streak of oily 
molecules. Generally I think the ducts, as seen in these specimens, are confined to 
the canals and fissures, but minute branches are often seen which just enter their 
substance for a little way ; I have never observed anything that in the least indi- 
cated that the ducts formed a plexus containing the cells in anastomosing tubes as 
described by Dr. Leidy. The opacity which renders the excretory ducts thus un- 
usually distinct, is occasioned by a deposit of minute oil-molecules between the nuclei 
which intercept the light ; this oily matter replacing in part the ordinary granular 
basis substance, and representing the oily matter which occurs so abundantly in the 
cortical renal tubuli of all London cats. 
* I request the reader to bear in mind that Mr. Lindsay Blyth’s experiments subjoined to this paper have 
fully shown that yellow pigment in the cells is not. at least commonly, any proof of the presence of true bile. 
The above was written before his experiments were performed. 
