276 NERVOUS SYSTEM. 



of repose. For this reason, we made our observation about 

 two hours after the first operation. To avoid the suspicion 

 of an extension of the galvanic current beyond the portion 

 of the cord which we desired to stimulate, the irritation was 

 first made by simply scratching the parts with the point of 

 a needle. The following experiment is the type of several, 

 in all of which the results were identical : 



May 28, 1863, at 1 P. M., the laminae and the spinous 

 processes of the three lower lumbar vertebrae were removed 

 from a medium-sized dog. There was no very great haem- 

 orrhage. The spinal cord and the roots of three of the 

 nerves were exposed, and the wound was then closed. The 

 operation was performed with the animal under the influ- 

 ence of ether, and lasted about three-quarters of an hour. 



About two hours after the first operation, the animal was 

 brought before the class at the Long Island College Hospi- 

 tal. The wound was opened, and the properties of the an- 

 terior and posterior roots were demonstrated. The follow- 

 ing observations were then made on the spinal cord : 



The external surface of the posterior columns was irri 

 tated by scratching with the point of a needle. This pro- 

 duced pain, the more marked, the nearer the irritation was 

 brought to the origin of the posterior roots. The surface 

 was almost insensible at the median line. A feeble galvanic 

 stimulus was then applied by means of a plnce electrique, 

 with the same results. The deep portions of. the posterior 

 columns were then irritated without effect. 



The cord was then divided transversely, and mechanical 

 and galvanic stimulus were applied to the cut surfaces. 



The surface of the upper end of the cord was irritated 

 with the needle, and the needle was plunged deeply into its 

 substance, without effect. The same negative results fol- 

 lowed application of the galvanic stimulus. 



The lower end of the cord was then elevated with a hook, 

 and the surface of the anterior columns was irritated by the 

 needle and by galvanism. The invariable effect was con- 



