ON THE SPINAL MARROW AND SPINAL NERVES. 185 
and sympathy of parts, and on which, in truth, not only the 
well-being of the system, but the proper action of every part 
depends. . « , 
The Motor Fibrils .—I can form a clearer conception of the 
anastomoses of the motor nerves. There is scaicely an action of 
the simplest nature that can be performed by the power of a single 
muscle. Many muscles must work together, and many nerves 
combine their influence, in order to its accomplishment. For the 
more perfect performance of this, and to secure the consentaneous 
action of these muscles, the fibrils of the nerves by which they are 
supplied are brought together, and have inter-communication 
with each other. A certain nerve is not only given to a certain 
muscle and there results only one contraction or action of that 
muscle, but the nerve spreads over the muscle, and enters into, 
and is diffused over, the substance of it; and, according to the 
part or division of the muscle on which its principal or only influ¬ 
ence is bestowed, the action is evidently and considerably vaiied. 
I can conceive, therefore, the necessity of the anastomoses of mi¬ 
nute branches, in order that, by the co-operation of parts of va¬ 
rious muscles, manv complicated motions may be effected. He 
who has a perfect knowledge of the anatomy and function of the 
muscles, could without much difficulty trace out any seemingly 
complicated arrangement of nervous fibrils. But we shall have 
other nerves by-and-by with which to associate those of sensa¬ 
tion and voluntary motion, and which will enable us moie satis¬ 
factorily to account for the intricacy ot their course. 
Comparative Survey of the Cervical Serves. I return to the 
nerves of the neck, and I find no material difference in any of 
our patients, except that the three first nerves are propoi tionally 
larger in the dog than m the horse, because they have compa¬ 
ratively bulkier and more powerful muscles to supply, and which 
are so placed as to act with greater mechanical disadvantage 
than in the horse. In the ox they are rather less developed 
than in the horse, for the neck is shorter, although the muscles 
are large. The number of pairs, namely eight, is the same in 
all of them, considering the suboccipital as the first. In our 
occasional patients—the domestic poultry—the number is greater, 
and varies in the different species: the common fowl has 14 
cervical nerves, the duck 15, and the goose 16. The pariot, 
respecting which we are sometimes consulted, has 12, and so 
has the lark, the goldfinch, and the canary, and most of our 
imprisoned warblers; and in all of them the nerves are propor¬ 
tionally larger than in quadrupeds. 
The Nerves of the Fore Extremities.— The sixth, seventh, and 
eighth cervical nerves, and the first dorsal, not only supply the 
