23-i NERVOUS SYSTEM. 



contract wlien a galvanic stimulus was applied to the branches 

 of the pneumogastrics. 1 



The main interest, in this connection, is attached to the 

 pulmonary branches and their relations to the respiratory 

 acts. These are undoubtedly connected with important re- 

 flex phenomena, acting as centripetal nerves ; and their di- 

 rect action in respiration is probably much less important. 

 They are exposed and operated upon in living animals with 

 so much difficulty, that we know little of the direct effects 

 of their irritation, and must judge of their general properties 

 chiefly by experiments showing their action upon respira- 

 tion. We shall have to study, in connection with the func- 

 tions of these nerves, the effects of their division upon the 

 lungs and the respiratory acts, and the phenomena, referable 

 to the respiratory organs, which follow their galvanization. 

 We shall also consider certain theoretical views with regard 

 to their action in the automatic processes of respiration, and 

 with the sense of want of air (besoin de respirer], which gives 

 rise to the reflex respiratory acts. 



Effects of Division of the Pneumogastrics upon Respira- 

 tion. Section of both pneumogastrics in the neck, in mam- 

 mals and birds, is usually followed by death, in from two to 

 five days. In young animals, death may occur almost in- 

 stantly, from paralysis of the respiratory movements of the 

 glottis, a fact which we have already noted in connection 

 with the recurrent laryngeal nerves. 8 In this connection, we 

 may note an interesting fact observed by Prof. J. C. Dalton, 

 of New York, who has succeeded in keeping dogs alive after 

 division of both pneumogastrics in the neck until complete 

 recovery took place. In several instances of this kind, after 

 killing the animals, Prof. Dalton found complete reunion of 

 the divided ends. 8 



Yery little of importance, with regard to the functions of 



1 LONGET, Traite de physiologic, Paris, 1869, tome iii., p. 535. 

 9 See page 222. 3 Oral communication. 



