893 



PAR VAGUM. 



and he has adduced in support of this view the 

 statement of Cruveilhier that after the function 

 of volition has been suspended by destroying 

 the cerebrum, the respiratory movements are 

 instantly arrested on dividing the vagi near 

 their origin.* In putting this opinion to the 

 test of experiment we found that though the 

 respirations were very much diminished in 

 frequency by the removal of the cerebrum 

 and cerebellum and then dividing the vagi, 

 they nevertheless continued for a longer or 

 shorter time.t Similar results have also been 

 subsequently obtained by Volkmann,^; by 

 Flourens, and by Longet.|| From these facts 

 we are entitled to conclude that the vagi are 

 not the sole exciters of respiration, and that 

 impressions may be made upon the medulla 

 oblongata capable of exciting the involuntary 

 respiratory movements after the vagi have been 

 divided in the neck, and when impressions 

 made on their expanded extremities in the 

 lungs can no longer be conveyed inwards to 

 the central organs of the nervous system. The 

 importance of the vagi as incident nerves of 

 respiration is not only proved by the marked 

 and immediate diminution in the number of 

 the respirations which follows their division,H" 

 but also in a more striking manner by the 

 morbid changes which take place in the 

 lungs. 



Morbid changes in the lungs after dividing 

 the vagi. The injury or division of the vagi is 

 almost always fatal after a few days, even when 

 precautions are taken to secure the free ingress 

 of air into the lungs. The period of death in 

 such experiments varies in different animals. 

 Rabbits generally die earlier than dogs. The 

 greater number of dogs die before the third 

 day, and comparatively few live beyond the 

 fifth day. In seventeen experiments upon dogs 

 we found that eleven died before the completion 

 of the third day, and seven of these eleven before 

 the completion of the second day. Longet 

 says that he performed this experiment on 

 thirty dogs, and they all died on or before the 

 fifth day, and none of the rabbits operated on, 

 lived beyond thirty-six hours.** Dupuy in 

 his experiments found that horses lived to the 

 fifth, sixth, and seventh day, when care was 

 taken to admit a sufficient quantity of air into 

 the lungs. ff De Blainville informs us that the 

 pigeons on which he operated died on the sixth 

 or seventh day;}} and in the experiments of 

 Arnold upon hens and pigeons, these animals 

 died between the second and fifth day. In 



tures on the Nervous System, p. 25. Memoirs on 

 the Nervous System, p. 87, 1837. 



* Lancet, 17th Feb., 1838, p. 733. 



t Opus cit. for 1839. 



j Opus cit. for 1840. 



Opus cit. Seconde edition, p. 204, Paris, 1842. 



|| Opus cit. torn, ii., p. 307, 1842. 



If A diminution of the number of respirations, 

 hut to a less extent generally, results from dividing 

 one of the vagi. 



** Opus cit. torn, ii., p. 306. 



tf Journal de Medeciue, Chirurg., &c., tome 

 xxxvii.,p. 356, Dec. 181ti. 



JJ Nouv. Bullet, de la Societ. Philom. tome i., 

 ann. ii., p. 226. 



$ Opus cit. s. 163. 



general the lungs are the only organs found in 

 an abnormal state after death from injury or 

 division of the vagi. We found the lungs 

 unfit for the healthy performance of their func- 

 tions in fifteen out of seventeen dogs experi- 

 mented upon. These organs are almost always 

 more or less congested with blood, especially at 

 the depending parts, and the bronchial tubes 

 and air cells frequently contain much frothy 

 serum. In some portions of the lungs the 

 congestion of blood is occasionally so great as 

 to render them dense and devoid of air. This 

 condensation is not unfrequently greater in 

 some parts than what can be accounted for by 

 the mere congestion of blood in the vessels, and 

 probably depends in a great measure upon the 

 escape of the solid parts of the blood into the 

 tissue of the lung. The frothy serum has fre- 

 quently a greater or less deep tinge of red. 

 Portions of the lung are likewise occasionally 

 found condensed from pneumonic effusion. 

 In seventeen experiments on dogs distinct evi- 

 dences of pneumonia were observed in five, and 

 in two of these it had run on to gangrene. 

 These morbid changes upon the lungs are suffi- 

 cient to explain the imperfect arterialization of 

 the blood, and the diminished evolution of 

 internal caloric which precedes death. We 

 have endeavoured to prove that these morbid 

 changes in the lungs are the result of the dimi- 

 nished frequency of the respiratory movements 

 which immediately follows the division of the 

 vagi. The vagi are the chief exciters of the 

 respiratory muscular movements, and when 

 they are tied or divided the respirations are 

 instantly diminished to less than half their 

 former number. The flow of blood through 

 the lungs is dependent upon the continuance 

 of the respiratory process, and the great dimi- 

 nution in the activity of the respiratory muscular 

 movements must be followed by a retardation 

 and congestion of the blood in the lungs. Such 

 a congestion of blood, as is well known, is 

 generally followed by an effusion of serum, 

 and also predisposes the organs so circumstanced 

 to various morbid changes, chiefly of an inflam- 

 matory nature. In the lungs this congestion is 

 not only followed by the escape of the serum, 

 but also of the more solid material from the 

 vessels, rendering the tissue dense. The ef- 

 fused serum is mixed up with air moving along 

 the bronchial tubes during inspiration and ex- 

 piration, and it thus becomes frothy. A little 

 blood may also exude from the congested mu- 

 cous membrane of the bronchial tubes, giving 

 the serum there effused a reddish tinge. As 

 these changes proceed, the respiratory process 

 becomes more and more imperfect, the blood 

 flowing along the arteries approaches more and 

 more to the venous hue, all the vital properties 

 of the tissue are enfeebled, the internal tempe- 

 rature sinks, and the animal dies of protracted 

 asphyxia. The division and other injuries of 

 the pneumo-gastrics have no direct effect upon 

 the production of the animal heat; they only 

 occasion this indirectly by enfeebling the func- 

 tion of respiration. We have elsewhere* ad- 



* Edinburgh Medical and Surgical Journal for 

 1839. 



