2 8o RESPIRATION 



rare instances they survive indefinitely. The most prominent symp- 

 toms (in the dog), in addition to the marked and permanent slowing 

 of respiration, quickening of the pulse and contraction of the pupils, 

 are difficult deglutition, accompanied by frequent vomiting and pro- 

 gressive emaciation. The appetite is sometimes ravenous, but no 

 sooner is the food swallowed than it is rejected ; and this is particularly 

 true of water or liquid food. Sometimes the rejected food is simply 

 regurgitated after having reached the lower end of the oesophagus, 

 without entering the stomach. The fatal result is usually caused, or 

 at least preceded, by changes of a pneumonic nature in the lungs. The 

 precise significance of the pulmonary lesion is obscure. But it would 

 seem that paralysis of the laryngeal and cesophageal muscles, with the 

 consequent entrance of saliva, food, or foreign bodies, carrying bacteria 

 into the lungs, is responsible to a great extent. And when only a partial 

 palsy of the glottis is produced, by dividing the right vagus below the 

 origin of the recurrent laryngeal, and the left as usual in the neck, pneu- 

 monia either does not occur or is long delayed. It may be that the tissue 

 of the lungs is rendered particularly susceptible to such insults in conse- 

 quence of trophic or vascular changes induced by section of the pul- 

 monary and cardiac fibres in the vagi. It may be quite clearly demon- 

 strated, however, in animals which live for some weeks, that, not- 

 withstanding the paralysis of the glottis associated with aphonia, no 

 pulmonary symptoms may be present till a day or two before death. 

 The picture presented in these cases is that of an animal suffering, 

 above all, from alimentary disturbances. The respiration is, to be sure, 

 very different from the normal in frequency, depth, and type, but there 

 is nothing to suggest that the lungs are the seat of any pathological 

 process. Suddenly the picture changes. Pulmonary symptoms ob- 

 trude themselves. The physical signs of consolidation of the lungs 

 may be detected, and in a short time the animal is inevitably dead. 

 Occasionally the determining cause of the pulmonary lesion seems to 

 be some external circumstance, as a sudden fall of the air temperature. 

 The idea is exceedingly apt to present itself to the observer that the 

 pneumonia is an accident, an acute intercurrent affection breaking the 

 course of a chronic malnutrition, which in any case must have ended 

 in death. Of course, the vagotomized animal is predisposed to this 

 accident, but there is no definite time after section of the nerves at 

 which it must take place. The vomiting is certainly connected with the 

 paralysis and consequent dilatation of the oesophagus ; and by previously 

 making an artificial opening into the stomach or by a surgical prophy- 

 laxis still more heroic, the establishment of a double gastric and 

 cesophageal fistula (p. 395), death may be prevented for many months. 

 Elimination of all the pulmonary fibres of the vagi, by extirpation of 

 one" lung, followed after an interval by section of the opposite vagus 

 in the neck, is not fatal in rabbits. This is also in favour of the view 

 that in double vagotomy the stress falls mainly on the digestive system. 



Innervation of the Bronchial Muscles. Both constrictor and 

 dilator fibres for the bronchi are contained in the vagus. They are 

 not constantly in action, but can be reflexly excited, most easily 

 (in the dog and cat) by stimulating the nasal mucous membrane, 

 and particularly a small area well back upon the nasal septum. 

 Cauterization of the corresponding area in man is said to give per- 

 manent relief in certain cases of spasmodic asthma, a condition in 

 which the recurrent attacks of dyspnoea seem, according to the most 



