THE LIVER AND ITS SECRETIONS. 
431 
have no duct opening into the alimentary canal ; but as soon 
as the blood, and consequently nutrition of the system, is to 
be produced from alimentary food by the process of digestion, 
then we find provision made for the pouring out of the bile 
into the intestine, so that it may mix with the aliment and 
begin the process of assimilation, which is perfected when 
brought back to the parenchymatous cells of the liver by the 
vena porta. But in the embryo, the whole of the process is 
carried on in the gland, for the obvious reason that the circu- 
lating fluid is provided by other means than digestion. And 
although Dr. Carpenter makes use of the fact, that the bile is 
found in the intestines, and forms a large part of the meco- 
nium discharged soon after birth, as a proof of its excremen- 
titious nature, yet I think we should be no more surprised to 
find it there ready prepared than we should to find milk in 
the mammae of the mother previous to parturition. 
That the liver is accessory to the formation of nerve- 
matter, I think is indicated by the fact that, in the class of 
lower animals in which we first detect a nerve-circle, we also 
first find the biliary apparatus as a separate gland (viz. the 
radiata), in which class also is the first special vascular circu- 
latory system ; and although there are biliary cells and folli- 
cles found in lower classes, yet I think that does not militate 
against my theory, for I imagine we ought not to expect to 
find a special nervous circle complete, though ever so limited, 
without having first a foreshadowing of it as a general secre- 
tion ; for we might as well deny assimilation to be going on 
in the lower animals because there are no vessels to carry the 
fluid to the parts, as to deny sensation because we cannot 
detect a complete nervous system. Indeed, I cannot imagine 
a mass of organic matter, as a whole endowed with animal 
life, without sensation ; and I think it would harmonise more 
with the general principles of comparative physiology to be- 
lieve, that nerve-matter may be diffused through the tissues, 
and that they are endowed with sensation as well as with the 
powers of assimilation. 
In the Crustacea, whose biliary cells are inclosed in follicles, 
it is observed that the cells which lie deepest in the coecum, 
contain, for the most part, the yellow granular matter, which 
may be regarded as the true biliary secretion ; but as they 
increase in size they also increase in the quantity of oil- 
globules which they contain, until beyond the middle of the 
follicle, where they are full of oil, so as to have the appearance 
of ordinary fat-cells. I think this proves that the bile enters 
into the composition of this fat, and as we find in the bile 
most of the components of nerve-matter, viz., soda, sulphur, 
