GENERAL PROPERTIES OF THE SPINAL CORD. 675 



The external surface of the posterior columns was irritated by scratching with the 

 point of a needle. This produced pain, the more marked the nearer the irritation was 

 brought to the origin of the posterior roots. The surface of the cord was almost insen- 

 sible at the median line. A feeble galvanic stimulus was then applied by means of a 

 pince electrique, with the same results. The deep portions of the posterior columns 

 were then irritated, but 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 followed 

 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 convulsive movements in the lower extremities, without pain. The same irritation 

 was applied to the deep portions of the anterior columns with like results ; viz., con- 

 vulsive movements in the lower extremities, following the irritation immediately. 



The above-mentioned phenomena were fully verified by repeated experiments, and 

 the animal was then killed by section of the medulla oblongata. 



The general movements accompanied by evidences of pain were readily distinguish- 

 able from the local convulsive movements with no pain. 



This experiment fully confirms the observations of Chauveau with regard to the pos- 

 terior columns, but it shows, in opposition to Chauveau, that the anterior columns are 

 excitable, both at the surface and in the deep portions. The recent observations of 

 Vulpian are also opposed to the results obtained by Chauveau with regard to the antero- 

 lateral columns. From a number of carefully-executed experiments, Vulpian draws the 

 following conclusions : 



u l. The gray substance is absolutely inexcitable. 



" 2. The anterior fasciculi possess a certain degree of motor excitability. 



"3. There is no doubt that the posterior fasciculi are very excitable. They are 

 sensitive and excito-motor if the cord be left intact, and simply excito-motor if the 

 cord be divided transversely and separated from the encephalon. It is the same, but 

 to a less degree, in that portion of the lateral fasciculi contiguous to the posterior 

 fasciculi." 



In the face of definite and positive experiments showing the excitability of certain 

 portions of the cord, it is impossible to accept the purely negative results obtained by 

 Chauveau and others. 



As the result of the most definite and reliable experiments of others, bearing upon the 

 question of the properties of the cord, and of our own observations, we have arrived at 

 the following conclusions: 



The gray substance is probably inexcitable and insensible under direct stimulation. 



The antero-lateral columns are insensible, but are excitable both on the surface and 

 in their substance ; and direct stimulation of these columns produces convulsive move- 

 ments in certain muscles, which movements are not reflex and are not attended with 

 pain. The lateral columns are less excitable than the anterior columns. 



The surface, at least, of the posterior columns is very sensitive, especially near the 

 posterior roots of the nerves. The deep portions of the posterior columns are probably 

 insensible, except very near the origin of the nerves. 



The above conclusions refer only to the general properties of different portions of the 

 cord, as shown by direct stimulation, in the same way that we demonstrate the general 

 properties of the nerves in their course. In all probability, the fibres in the white and 

 gray substance of the central nervous system conduct motor stimulus from the brain and 

 sensory impressions to the brain, while they themselves may be insensible and inexcit- 

 able under direct stimulation. 



