PNEUMOGASTRIC, OR PAR VAGUM NERVE. 665 



upon the intestinal canal, for the reason that the distribution of the abdominal branches 

 to the small intestine, notwithstanding the researches of Kollmann, in 1860, does not 

 appear to have been generally recognized. The right, or posterior abdominal branch was 

 formerly supposed to be lost in the semilunar ganglion and the solar plexus, after sending a 

 few filaments to the stomach ; but, since it has been shown that this nerve is supplied to 

 the whole of the small intestine, its physiology, in connection with intestinal secretion, 

 has assumed considerable importance. 



In a series of experiments, by Prof. Horatio C. Wood, Jr., of Philadelphia, the impor- 

 tance of the abdominal branches of the right nerve is fully illustrated. These experi- 

 ments show, in the most conclusive and satisfactory manner, that the pneumogastrics 

 influence intestinal as well as gastric secretion. One of the most interesting and curious 

 points in connection with their function is that, after section of the nerves in the cervical 

 region, the most powerful cathartics, croton-oil, calomel, podophyllin, jalap, arsenic, etc., 

 fail to produce purgation, even in doses sufficient to cause death. The articles used were 

 either given by the mouth, just before dividing the nerves, or were injected under the 

 skin. 



Although the observations of Dr. Wood are not entirely new, they are by far the most 

 extended and satisfactory, and were made with a knowledge of the fact of the distribu- 

 tion of the nerves to the small intestine. Dr. Wood quotes freely from the experiments 

 made by Sir Benjamin Brodie and by Dr. John Reid. Brodie failed to produce purging 

 in dogs, when both pneumogastrics had been divided in the neck, after the administration 

 of arsenic by the mouth and after injecting it under the skin. Dr. Reid made five experi- 

 ments, and, in all but one, it is stated that diarrhoea existed after division of the nerves. In 

 twenty experiments by Dr. Wood, there was no purgation after division of the nerves, in 

 one there was free purgation, and in one there was " some slight muco-fecal discharge. 1 ' 

 From these, Dr. Wood concludes that, while section of the cervical pneumogastrics, in 

 the great majority of instances, arrests gastro-intestinal secretion and prevents the action 

 of purgatives upon the intestinal canal, a few exceptional cases occur in which these 

 effects are not observed. 



The facts just mentioned are exceedingly interesting in connection with the experi- 

 ments of Traube upon the action of digitalis after section of the pneumogastrics. It will 

 be remembered that, in these experiments, digitalis failed to diminish the number of beats 

 of the heart when the nerves had been divided in the neck, showing that the separation 

 of the heart from its connections with the cerebro-spinal system removed the organ from 

 the peculiar and characteristic effects of the poison. 



It would be interesting to determine whether the pneumogastrics influence the intes- 

 tinal secretions through their own fibres or through filaments received from the sympa- 

 thetic system ; but there are no experimental facts sufficiently definite to admit of a posi- 

 tive answer to this question. If the action take place through the sympathetic system, 

 as in the case of the stomach, the filaments of communication join the pneumogastrics 

 high up in the neck. 



