368 



For I could hardly doubt that the cause of the quiescence of the 

 heart or intestines on irritation of the vagus or splanchnic nerves 

 was analogous to that of arterial dilatation in the web, and that, 

 provided a sufficiently mild stimulus were applied to the so-called 

 " inhibitory nerves," increased action of the viscera would occur, 

 corresponding to the vascular constriction. 



To test the truth of this hypothesis, I made several experiments 

 between the 17th of June and the 14th of July of this year, with re- 

 gard to the movements of the heart and intestines. The means 

 used for stimulating the nerves and spinal cord were sometimes me- 

 chanical irritation, but more commonly galvanism, applied with a 

 magnetic coil battery of a single pair of plates, the strength of which 

 could be regulated in a rough way, with great facility, by the height 

 at which the acid solution stood in the jar and the extent to which 

 the rods of soft iron were inserted in the helix. The mildest action 

 employed was such as was but just perceptible to the tip of the 

 tongue, placed between the fine silver-wire extremities of the poles, 

 when the rods were fully in the helix, but inappreciable after their 

 complete withdrawal ; the spring carrying the magnetic bar being 

 made to vibrate by a touch with the finger : the greatest action of 

 the battery, on the other hand, was so powerful as to elicit sparks 

 when the poles were applied to the tissues. 



My attention was first directed to the intestines, and it may be 

 well to mention first all the results obtained with reference to them. 

 The animals operated on were generally rabbits, they being very 

 easily managed, and also favourable for the purpose on account of 

 the large amount of movement which occurs in their intestines. 

 Chloroform was generally not administered, on account of its de- 

 pressing effect upon the action of the nervous centres. 



In the first experiment, the ends of the poles having been fixed 

 to the spinous processes of the ninth and twelfth dorsal vertebrae, 

 according to Pfliiger's original method, and the intestines allowed to 

 protrude through a wound in the abdominal parietes, a series of in- 

 terrupted currents were transmitted, a very small amount of acid 

 being in the jar, and the rods fully in the helix. The effect was 

 complete relaxation and quiescence of the small intestines, which had 

 been previously in considerable movement, while the muscles of the 

 limbs were thrown into spasmodic action ; but on the discontinuance 



