368 PHYSIOLOGY. 



Good has tried artificial inflation on animals with excellent results, 

 and proposes this procedure as a method of treatment in these cases 

 of trigeminal inhibition. 



Mechanical stimulation of the sensory nerves is sometimes 

 resorted to by midwives. It is well known that to arouse a sluggish 

 respiratory center they resort to slapping the buttocks of a newborn 

 child. 



During the act of deglutition there is a very necessary cessation 

 of breathing for a short period. This is caused by stimulation of 

 the central end of the glosso-pharyngeal nerve. 



Section of the cord just below the medulla produces an arrest 

 in the movements of not only the intercostals, but even the dia- 

 phragm. Section of one phrenic nerve paralyzes the corresponding 

 half of the diaphragm; division of both nerves causes entire cessa- 

 tion of movement of the diaphragm. The phrenic nerves take an 

 active part in the function of respiration. When these nerves are 

 bared and irritated there is noticed a rapid movement of the 

 abdomen produced b contraction of the diaphragm. The spasmodic 

 movement is repeated at each irritation so long as the tissue of the 

 nerve remains uninjured. If instead of mechanical, an electrical 

 irritant be applied, the diaphragm is thrown into a state of tetanic 

 contraction and produces death from asphyxia. As the irritability 

 of the phrenic nerve remains a long time after death, it becomes 

 easy to demonstrate these phenomena without causing any pain. 



After section of the vagi the heart's movements become more 

 rapid and the respirations slower. At the end of some minutes the 

 nares dilate a little, inspiration is accompanied with a slight noise, 

 an indefinite restlessness seems to seize upon the animal from head 

 to foot; it moves about frequently, and raises and lowers the head 

 as if there was a constriction of the throat. At length the anxiety 

 of the animal disappears; it is calm and quiet; respiration is slow 

 and the beats of the heart augment in frequency. Finally the ani- 

 mal dies from an affection of the lungs known as vagus pneumonia, 

 due to removal of trophic vagi fibers of the lungs. The slow respira- 

 tion is due to removal of afferent impulses in the section of vagi. 

 For a time after the section the amounts of carbonic acid exhaled and 

 of oxygen taken in remain ' the same, but finally they are much 

 changed. The animals usually live seven days, but Pawlow has suc- 

 ceeded, by dividing one vagus and then waiting some time before 

 dividing the next one, in keeping them alive. 



Instead of tying or dividing the vagi, a galvanic current may be 



