128 
DR. C. H. JONES ON THE STRUCTURE 
before it can be received into the excretory duct ; and lastly, if correct, they seem to 
establish that the liver is not widely removed from the class of g-lands destitute of 
efferent ducts, like them allowing a part of its elaborated products to return at once 
into the blood, from whence as plasma they had been derived. On a future occasion 
I trust to have the opportunity of examining more closely into the function of the 
liver. I may however at present remark, that if the capillary radicles of the portal 
vein absorb the saccharine and amylaceous matters from the intestines, it seems a 
wise provision that the blood so charged should percolate intimately a vast mass of 
cells, which may specially act on the newly-absorbed materials, retain them if they 
are in excess, convert them into biliary compounds, and again allow them to return, 
as needed, into the circulating current : this in fact is nearly the view proposed by 
Messrs. Bouchardat and Sandras. I have, lastly, to speak of the relation which the 
excretory ducts, before described, hold to the lobules of the parenchyma. As far as 
I can ascertain, they do not ramify very extensively, at least both in the Rabbit and 
Sheep many fissures appear quite destitute of them ; in those where the margin is in 
an active state, the cells bare and discharging their contents, the absence of the duct 
may often I think be clearly determined; in others, where the margin is still covered 
by the investing membrane, it is more difficult to be certain, but generally I think it 
maybe stated that they do not extend far beyond the “spaces;” here however I have 
in thin sections several times distinctly observed small ducts which terminated by 
closed extremities. In the portal canals small duct branches creep over the surface 
of the parietal lobules, and take up their elaborated products. In now endeavouring 
to determine the mode in which the biliary secretion formed exterior to the ducts 
arrives in their interior, we may recall with advantage the condition of the gland, as 
we found it to exist in the class of Fishes. Here it was seen that the excretory ducts, 
having coats of great tenuity and containing an active epithelium in their interior, 
ran a long course imbedded in the parenchyma, and bathed as it were in its copious 
secretion ; moreover, coincidently with the assumption of the parenchymal form, we 
found that a separate vessel conveying a different kind of blood was appropriated to 
the nutrition of the hepatic duct and its branches, and it seems certain that a dif- 
ferent material is formed in the interior of the excretory ducts, from that which is 
produced so abundantly around them. May it not therefore be considered as far 
from improbable, that the absorption of the secreted material is effected by an action 
of endosmotic character, not however one of mere physical kind, but vital, i.e. pecu- 
liar in its nature, and producing, I believe, at the same time a change more or less 
considerable in the fluid absorbed*? One further proof may be adduced in the class 
* It may be observed, that, supposing the nucleus to be the essential agent in the elaboration of all secretions, 
the structural condition of the ultimate hepatic ducts is just that, which is best fitted for the office I believe 
them to fulfill, of eliminating from the product of the surrounding cells the bile itself : moreover this condition, 
which might in some measure be regarded as the natural result of their diminution in size, corresponds pre- 
cisely with what seems to be required by the function ascribed to them, — an accordance such as is rarely seen 
except in the actual works of nature herself. 
