472 mr. vouatt’s veterinary lectures. 
propelled through the intestinal canal, if there were not a power 
by which it is dissolved and changed, and its valuable parts 
separated, and prepared to become blood. The arterialization of 
that blood is a mere mechanical and chemical affair. It is ex¬ 
posed to the action of the atmosphere, and it undergoes a change 
for which the simple principles of chemistry will enable us to 
account: but, thus arterialized, it would permeate the greater 
and the lesser vessels to no purpose, if there were not a power by 
which, in the minuter capillaries, it is assimilated into the sub¬ 
stance of the frame, and many a strangely varied secretion is per¬ 
formed. This is the power for which we are now seeking. No 
beautiful adjustment of various parts, no exquisite consent of 
motion between them, can accomplish this. No chemistry will 
here avail; we may trace its agency to a certain extent, but as 
we proceed we find its most invariable and energetic laws sus¬ 
pended—subverted. There is a principle still wanting. We must 
not look for it in the brain : if the mere mechanical part of organic 
life was in a manner independent of the will (at least in its most 
essential function it was so), this most important portion of organic 
life must be perfectly so: and so it is. Not only are we un¬ 
conscious of the solution and chylification of the food, and the 
performance of the various secretions, but let every mental 
“ agent” be “bent up” to the terrible feat of arresting or ma¬ 
terially interfering with the organic process, we should be per¬ 
fectly powerless. Where, then, shall we go ? 
It is the Nutritive or Secretory Nerve .—There is a nerve, the 
function of which we have not yet determined—the sympathetic 
or great organic nerve. On what tissue are its ramifications 
chiefly expended ? It is scarcely found ere it is forming com¬ 
plicated plexuses on every neighbouring bloodvessel; it is so 
even within the cavernous sinus; it is enclosing the carotids, 
external and internal, with a kind of nervous tunic. I trace it 
round the temporal to the face and head, and also on every sub¬ 
division of the carotid, until, from the minuteness of the vessel; 
and the pulpiness of the nerve, it eludes my sight. I trace it 
into the thorax, and its ramifications are given to large blood¬ 
vessels there: I can follow it in the branching of every vessel; 
and, in the very substance of the viscus, filaments or plexuses of 
the organic nerve accompany the tube. I examine its course 
when it enters the abdominal cavity, and there too it is on the 
roots of the different arteries that the plexus is first observed, 
and it accompanies the ramifications of each artery to its ulti¬ 
mate destination. Where it ceases I know not. That it ac¬ 
companies and envelopes the capillaries I dare not affirm; but 
as I gradually lose it through want of visual power to pursue it, 
