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DR.' A. WALLER ON THE ALTERATION OF THE 
it is my intention at present to describe various alterations, as seen under the micro- 
scope, which take place in the structure of the same nerves after their continuity 
with the brain has been interrupted by section. The innervation of the frog’s tongue 
is, as I have already shown, derived from two pairs of nerves, one arising from the 
brain, and traversing a foramen in the posterior part of the cranium, accompanied by 
the pneumogastric nerve. This pair corresponds to the glossopharyngeal in Man. In 
its course it descends until it reaches the hyoglossus muscle, when it is accompanied 
by the lingual vessels passing over part of the hyoid bone, and entering the tongue 
without giving off any branch to the throat. The other pair arises from the anterior 
part of the spinal marrow, traverses the first cervical foramen, and constitutes the first 
cervical pair of nerves. Following the example of Burdach, I regard this pair as 
corresponding to the hypoglossal in Man, and shall apply that term to it. It takes its 
course towards the tongue in a similar direction to that of the former pair, giving off 
several branches to the muscles of the neck and throat, and when it reaches the hyo- 
glossus muscle it is considerably smaller than the glossopharyngeal. After attaining 
this muscle it runs parallel to the former nerve, passing below the hyoid bone in its 
transit to the tongue. For a more minute description I must refer to the paper of 
E. Burdach, of which a translation has appeared in the Annales des Sciences Natu- 
relles. 
Division of the Glossopharyngeal Nerve. 
That division of these nerves produces some serious lesion is proved by the death 
of the animal, which generally takes place a few days after the operation. Consider- 
ing the well-known tenacity of life possessed by these animals this was quite an un- 
expected result, for which I am unable at present to afford any satisfactory reason. 
We can only surmise, that besides their gustatory powers, they have others connected 
with respiration, in regulating the action of the tongue in closing the nares, for forcing 
the air into the lungs. Whatever may be the true explanation, it is impossible not 
to regard this result with surprise, when we consider the serious lesions which this 
animal is capable of undergoing at other points of the frame without loss of life. The 
usual time which it survives is variable, and depends greatly on the season of the 
year. If the examination takes place in summer, death frequently ensues on the 
fifth day ; if in winter, not before the twentieth. For the purpose of avoiding this 
loss of life, I adopt the plan of dividing the glossopharyngeal on one side only of the 
tongue, and I find that it has the desired effect of preserving the life of the animal, 
while we can observe the same alterations on the corresponding side, as well as when 
both nerves are divided. Another advantage found in the division of a single nerve 
is, that on the uninjured side we have constantly at hand a means of comparison by 
which we can judge with certainty respecting any alterations that may be produced 
in the divided nerve. In cases of any doubt, it will always be found of the greatest 
service to examine at the same time a minute fragment from each side of the tongue. 
The first effects of section of a glossopharyngeal nerve at the throat, are decreased 
