NERVOUS SYSTEM. 



fully in detail, but shall refer simply to certain of them, made within a few years with 

 the advantage of a knowledge of the reflex phenomena following irritation of the cord, 

 which must always be taken into consideration in such experiments. 



In 1861, Chauveau, as the result of numerous experiments performed upon horses, 

 cows, sheep, goats, rabbits, pigs, dogs, and cats, stated that the antero-lateral columns 

 of the cord were inexcitable, both on the surface and in the deep portions. The facts 

 upon which this assertion was based were, that direct stimulation of these portions of the 

 cord in living animals, whether by mechanical means or by feeble galvanic shocks, pro- 

 duced no contraction of muscles and no pain. Upon irritating the posterior columns, 

 either by mechanical or galvanic stimulus, Chauveau noted pain and reflex movements 

 when the irritation was applied to the surface, but the results were negative when the 

 deep portions of the columns were operated upon. The surface of the posterior columns 

 seemed to possess the same general properties as the posterior roots of the nerves, espe- 

 cially near the roots, where the sensibility was most marked, gradually diminishing in 

 intensity toward the median line ; but the deep portions of the cord were everywhere 

 found completely insensible and inexcitable. 



The experiments and conclusions of Chauveau have a most important bearing upon 

 the physiology of the cord, and they are opposed to the views of the majority of physio- 

 logical writers, although they have been admitted by some experimenters. We shall dis- 

 cuss first the experiments upon the antero-lateral columns, which are most remarkable 

 in their negative results. We shall use the term excitability as signifying the property of 

 the cord which enables it to conduct a stimulus applied directly to it to certain muscles, 

 producing convulsive movements confined to these muscles, and not of a reflex character. 

 We shall apply the term sensibility to the property by virtue of which an irritation directly 

 applied is conveyed to the brain and produces a painful impression. 



The experiments of Chauveau and some others upon the antero-lateral columns are 

 simply negative ; but their results are directly opposed to those of numerous experimenters, 

 who have produced local and restricted convulsive movements by direct irritation of both 

 the superficial and the deep portions of these columns. 



With regard to the posterior columns, the views of Chauveau are in advance of those 

 of previous observers, only in so far as he has shown that, although the surface of this 

 portion of the cord is endowed with sensibility, its deeper portions are entirely insensible, 

 except in the immediate proximity of the posterior roots of the nerves. 



In view of the importance of the question under consideration, and of the contradic- 

 tory results of experiments, we repeated, in 1863, the experiments of Chauveau, under 

 conditions as nearly physiological as possible. We had often had occasion to note the 

 diminished sensibility of the roots of the spinal nerves immediately following the very 

 severe operation of opening the spinal canal, and had also noted that the sensibility 

 increased, probably approaching the normal standard, after the animal had been allowed 

 a few hours of repose. For this reason, we made our observations 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 

 haemorrhage. 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 tinder the influ- 

 ence of ether, and it 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 Hospital. The wound was opened, and the properties of the 

 anterior and posterior roots were demonstrated. The following observations were then 

 made upon the spinal cord: 



