140 FUNCTIONS OF THE NERVOUS SYSTEM. 



the respiratory movements, whether it be performed before or after the section 

 of the Vagi. Dr. Reid found that, in a kitten of a day old, in which the inspira- 

 tions were 100 per minute, they fell to 40 when the Encephalon was removed ; 

 and on subsequently cutting the Pneumogastrics, the number of inspirations 

 instantly fell to between 3 and 4 in the minute, and continued so for some 

 time. Hence it appears that the respiratory movements are partly dependent 

 upon cerebral agency or volition ; and this may also be learned from the pro- 

 longed and laborious character of the inspirations during sleep or profound 

 attention, when the influence of the Cerebrum is more or less suspended. 



185. But why (it may be asked) do the movements continue, when the 

 Pneumogastrics have been divided, and the Encephalon has been removed? 

 It is evident that there must be other exciters to the action of the respiratory 

 muscles. Amongst these, the nerves distributed to the general surface, and 

 particularly to the face, probably perform an important part ; and in exciting 

 the first inspiration, the Fifth pair seems the principal agent. It has long been 

 a well-known fact, that the first inspiratory effort of the new-born infant is 

 most vigorously performed, when the cool external air comes into contact with 

 the face ; and that impressions on the general surface, such as a slap of the 

 hand on the nates, are often effectual in exciting the first inspiratory move- 

 ments, when they would not otherwise commence. Dr. M. Hall relates an 

 interesting case, in which the first inspiration was delayed, simply because the 

 face was protected by the bed-clothes from the atmosphere ; and, on lifting up 

 these, the infant immediately breathed. Dr. M. Hall has recently mentioned 

 the important fact, that if the cerebrum be removed and the pneumogastrics 

 be divided in a young kitten, the number of acts of respiration will be reduced 

 to four in a minute ; but by directing a stream of air on the animal, or by irri- 

 tating various parts of the general surface, we may excite twenty or thirty acts 

 of respiration within the same space of time. He further remarks, that in the 

 very young warm-blooded animal, as in the cold-blooded animal, the pheno- 

 mena of the excito-motor power are far more vividly manifested than in the 

 older and the warm-blooded. In the very young kitten, even when asphyxi- 

 ated to insensibility, every touch, contact, or slight blow, every jar of the 

 table, any sudden impression of the external air, or that of a few drops of cold 

 water, induces at once energetic reflex movements, and acts of inspiration. 

 This may be looked upon as Nature's provision for the first establishment of 

 the acts of inspiration in the new-born animal. But the influence of the nerves 

 of the general system is by no means wanting in the adult ; as the following 

 experiment of Dr. J. Reid's demonstrates. After dividing the pneumogastrics, 

 and removing the cerebrum and cerebellum, he divided the spinal cord high 

 up in the neck, so as to cut off the communication between the spinal nerves 

 and the Medulla Oblongata ; and he found that the frequency of the respira- 

 tory movements was still further diminished, although they were not even 

 then entirely suspended. Every one knows the fact, that the first plunge into 

 cold water, the first descent of the streams of the shower-bath, or even dashing 

 a glass of cold water in the face, will produce inspiratory efforts ; and this fact 

 has many important practical applications. Thus, in the treatment of Asphyxia, 

 whether congenital or the result of narcotic poisoning, drowning, &c., the 

 alternate application of cold and heat is found to be one of the most effica- 

 cious means of restoring the respiratory movements; and a paroxysm of hys- 

 teric laughter may be cut short by dashing a glass of cold water in the face. 

 It may be surmised that the Sympathetic nerve, which derives many filaments 

 from the Cerebro-Spinal system, and which especially communicates with the 

 Pneumogastric nerves, is one of the exciters to this function; and this, per- 

 haps, not only through its ramifications in the lungs, which are considerable, 

 but also by its distribution on the systemic vessels ; so that it may convey to 



