14 
DR. C. H. JONES ON THE STRUCTURE, DEVELOPMENT 
It must be sufficiently apparent how essentially similar the development of the 
liver and its apparatus of efferent ducts is found to be in the three lower vertebrate 
classes. Hitherto I have not been able to pursue the examination in Mammalia ; and 
though I am aware that Bischoff’s account of it in this class is in accordance with 
the view of its being a protrusion from the intestine, yet I must remark that the pro- 
cess, as being conducted more slowly in the lower classes, is more favourable for cor- 
rect observation, and that it seems unlike the known unity of scheme which charac- 
terizes the works of Nature, to find an essential difference in one class from that 
which prevails in the three others. 
I have little to add to the anatomical account I previously gave of the condition of 
the liver in Mammalia ; I have studied it recently more particularly with a view to 
the elucidation of its function, and will now only touch on those points which bear 
upon this matter. One most important question to determine positively is where the 
bile is in the healthy state necessarily formed; whether in the cells of the parenchyma, 
or in the ultimate hepatic ducts. The prevalent opinion among physiologists certainly 
is that the bile is actually and necessarily formed in the hepatic cells ; they are con- 
sidered homologous to those of the renal tubuli, and on account of this homology 
and a certain not very manifest yellowish tint, it is usually held that the bile is 
primarily formed in them, and liberated by their dehiscence in the cavity of the duct. 
From this opinion, which I long held unquestioningly, and to which I have often 
referred, observation alone inclines me in some measure to dissent. I have scrutinized 
numerous specimens of the livers of our ordinary domestic animals with a view to 
determine this point, and still cannot convince myself that bile is present in the 
parenchymal cells as a normal and necessary condition. If present, it ought not to be 
very difficult of detection, seeing that it is a coloured fluid, and that the cell which 
contains it is in this class generally provided with a distinct envelope : it ought, in 
fact, to be as apparent, or nearly so, as it is in the cells of the follicular livers of Mol- 
lusca. But this is not the case; according to my observation the cells commonly 
appear as pale granulous nucleated particles, with a more or less distinct limiting 
envelope, and presenting a few or perhaps numerous and large oil-drops amid the soft 
albuminous mass. Not unfrequently a distinct yellow fluid is seen infiltrating the 
granulous contents, or several yellow highly refracting drops are observed in the 
same situation ; this indicates of course that bile is present in such particles, but they 
are seldom seen except when the liver is in a state of so-called biliary congestion. 
This condition is consequently most often observed in human livers. The cells, when 
massed together and viewed by transmitted light, very commonly, perhaps always, 
produce a kind of reddish yellow tint ; but this seems to me to differ decidedly from 
the yellow tint of bile, and to be probably dependent on some diffused hematin 
tinging the cells, or on some modification which the light has undergone by unequal 
refraction in its passage through the mass; at any rate I could not, were I advocating 
the opposite opinion, rely on it for a moment as sufficient evidence of the presence of 
