29 8 Mr. Bell on the nerves which associate the muscles 
that to excite the actions of these muscles, it was necessary to 
compress the nostrils. When they began to act with more 
violence, keeping time with the actions of the other muscles of 
respiration, the superior respiratory nerve was divided ; im- 
mediately the action ceased in the muscles attached to the 
sternum of the side where the nerve was divided, while the 
corresponding muscles of the other side continued their 
actions. 
After dividing the spinal marrow between the vertebrae of 
the neck and those of the back, respiration is continued by the 
diaphragm : which experiment, as it is often mentioned by 
physiologists, the author has not thought it necessary to re- 
peat, but only to institute the following experiment on an ass. 
The phrenic nerves being first divided, and then the spinal 
marrow cut across at the bottom of the cervical vertebrae, 
respiration was stopt in the chest; but there continued a 
catching and strong action at regular intervals in the muscles 
of the nostrils, face, and side of the neck. The main part 
of the apparatus of respiration was stopped, but these ac- 
cessory muscles remained animated, and making ineffectual 
endeavours to perform the respiration. When apparent 
death had taken place, the ass was re-animated by artificial 
breathing, and then these muscles on the face and neck were 
restored to activity, and became subject to regular and suc- 
cessive contractions, as in excited respiration, whilst the chest 
remained at rest. These actions continued for a short time, 
and then ceased ; but upon artificial respiration being again 
produced, the same results followed. This was repeated 
several times, the animal remaining insensible during these 
experiments. 
