DR. MOXON, ON MOTOR NERVE. 239 
Mr. Hilton, that the nerves of muscles are large in propor- 
tion as the muscles are required to be in frequent or con- 
stant operation, and, I may add, as their action is delicate. 
For the first proposition the large nerves of the sphincter ani 
and of the deltoid, with the other muscles whose constant 
operation is needed to maintain the apposition of the bones 
at the shoulder-joint, will serve as illustrations; for the second, 
the size of the nerves of the muscles of the eyeball and 
larynx. Another general law of the relation of muscle to 
nerve is also prettily illustrated in this instance, the same 
nerve supplies the sensory organ and the muscle which 
moves it, just as in human anatomy the nerve which supplies 
a muscle supplies also the part moved. 
The muscle-fibre is so far separated from others, the space 
about it is so clear, and its direction so different from that 
of any other fibre in its remote vicinity, that no doubt could 
exist about any further continuation of the nerve-fibre, such 
as is described by Dr. Beale, if such continuation existed, and 
this assurance is further verified during the contraction of the 
muscle, for then the nerve-fibre is drawn up and down, so that | 
whilst its connection with the muscle is put beyond doubt, 
its freedom from any other connection is made certain; any 
other connection, if present, must at once strike the eye 
during movements of the muscle and nerve among quiescent 
parts. 
Whether the nervous elements are throughout distinct 
from the muscular, or whether they join and unite with them, 
is a question of prime importance to any apprehension of the 
manner of action of nerve upon muscle. It was long ago 
surmised, and the supposition still lingers, that the loops of 
nerve believed to cross the muscle-fibres might induce in 
them contraction, as cross currents of electricity cause _ 
magnetic phenomena. If the view put forth by Dr. Beale 
were correct this theory might still find place, but the direct 
ending of nerve-fibres iz muscle-fibres does away entirely 
with the analogy, an analogy which, though attractive, was 
never satisfactory, because it could not be shown how the 
current supposed to course in the nerve-fibres could be imsu- 
lated. 
In conclusion, I would remark the proof of a direct ending 
of nerve upon striated muscle-fibre in a single case must hold 
good for all cases alike, for I submit that no one can suppose 
that sometimes the nerve does go into the muscle and some- 
times it does not. 
Nothing in all the history of Nature is so astonishing as 
the identity of the constructive elements of the most different 
