AND DEVELOPMENT OF THE LIVER. 
121 
voirs in part for the immense quantity of oily matter which is produced in the 
gland. 
Turning now to the examination of the parenchyma of the liver in Fishes, it may 
be stated that it does not usually present a very marked division into lobules ; this 
however is often indicated by the branching of the vessels, which do not run in inter- 
lobular fissures, such as exist in the liver of mammals. The term parenchyma is in 
the greater number of instances exactly expressive of the condition of the secreting 
portion of the hepatic apparatus in fishes, it is truly a substance poured among and 
upon the vessels and ducts, filling up completely the interstices between them, and 
forming together with them a solid mass ; its actual state may vary a good deal ; 
sometimes the greater part consists of perfect cells with distinct envelopes, and there 
is only a small quantity of free nuclei with granular and oily matter ; at other times 
these are found to predominate, and but few perfect cells are to be detected ; in this 
case however we very commonly observe a tendency to the formation of cells, the 
granular and oily matter being aggregated into cell-like masses, which either enclose 
or have enclosed at some time a nucleus. The masses of biliary granules, which I 
have already mentioned as adhering to the ducts, occur also free in the parenchyma; 
besides these, I have found in the Mackerel {Scombriis Scomber), and also in the 
Flounder {Platessa Jtesus), some peculiar cells which are perhaps of the same nature 
as the above-mentioned masses ; they are larger than the secreting cells, of a perfectly 
circular form, and contain, within a well-marked envelope, from three to five oval or 
subcircular vesicles, which have often a nucleolar corpuscle in their centre, and 
possess a high refractive power; these cells lie free in the midst of the parenchyma, 
often forming small groups, which are imbedded in yellowish granular matter. 
The Flounder furnishes an exception in some measure to the rule, that the liver of 
fishes is not divided into lobules by fissures ; the last twigs of the portal vein may be 
distinctly traced running in canals and short fissures in thin sections of the organ, 
these canals being much wider than the vessels contained in them ; hence arises in 
certain conditions of the gland a remarkable disposition which is well worthy of 
notice. I have usually found the parenchyma of the liver in this fish of a yellowish 
white colour, and very opake from the great quantity of oily matter contained in it ; 
but sometimes it is found much more transparent and of a^ redder tinge ; in the former 
of these conditions the canals and fissures are comparatively empty, but in the latter 
they are filled with cells of about the same size as those of the parenchyma, but 
more opake and of a darker aspect from the oily nature of their contents. The inter- 
pretation which I would offer of this appearance is, that in this state the parietal cells 
of the canals and fissures do not readily dehisce and discharge their contents into 
the cavity, from whence they may be absorbed by the excretory ducts, but encroach 
upon and fill it up : we shall find in Mammalia instances of a somewhat similar 
occurrence, which appear to me particularly significant of the real constitution of 
the liver. 
MDCCCXLIX. 
R 
