514 
C. Influence of severing the sensitive roots of N. cervicalis 
1 and 2 on the tonic cervical refleves on the eyes. 
As stated heretofore, Barany supposed his reflexes to be cervical 
reflexes, but difficulties with regard to the technique prevented him 
from demonstrating this. These difficulties were known also in our 
Institute. In experiments with cats and dogs previously published 
by Magnus and Storm van Luguwen’) the tonic cervical reflexes on 
the skeletal muscles were eliminated by severing the sensitive roots 
of the Nn cervicales 1, 2, and 8. This could be readily done with 
cats, but with rabbits it was extremely difficult. It is rather easy 
to get at the roots of cervicalis 1 by splitting the membrana atlanto- 
occipitalis. By the help of suitable focal illumination the sensitive fibers 
will be seen to run along freely, and with the aid of a hook they 
can be easily pulled through. If, as will sometimes happen, the 
operation causes hemorrhage from a vein somewhere about the 
fibers, the operation should be discontinued, as in that case there is 
no knowing whether it has been fully accomplished. The sensitive 
root of cervicalis 2 can be reached outside the spinal column; the 
section of this root is rather simple. The difficulties arise only with 
the effort to sever the sensitive root of cervicalis 3. This must be 
effected in the spinal column and in this process the hemorrhage is 
often so profuse that the animal succumbs already during the opera- 
tion. This was shown also by Maenus and Storm van LEEUWEN’s 
researches, in which the researchers succeeded only twice in keeping 
the animals alive after this operation. 
We did not think it proper to sacrifice again a large number of 
animals and first wished to study the cervical reflexes after severing 
the sensitive roots of cervicalis 1 and 2. The experiments were 
conducted in the following way: First bilateral extirpation of the 
labyrinth in order to completely eliminate the tonic labyrinth reflexes. 
After a few days the animals were examined closely for tonic cer- 
vical reflexes. Only of those animals that showed distinctly the tonic 
cervical reflexes on the eyes, the sensitive roots of C. 1 and 2 were 
cut through. This was to the following effect. 
In one animal the tonic cervical reflexes had quite disappeared 
after the sensitive roots of Nn cervical. 1 and 2 had been cut through ®). 
1) R. Maenus und W. Storm v. Leeuwen. Die akuten und die dauernden Folgen 
des Ausfalles der tonischen Hals- und Labyrinthreflexe. Pflügers Arch. 159. 157. 1914. 
2?) In one other animal the tonic reflexes could still be evoked in a small mea- 
sure. After section it appeared that on either side of the N cervicalis 1 a fibril 
was left behind. 
