ON THE MAMMALIAN NERVOCS SYSTEM. 429 



It is thus clear that in the etherised animal the excitatory electrical change is con- 

 ducted along the structures on the same side of the cord as the excited nerve, and if 

 the effect is a true indication of the passage of nerve impulses along nerve fibres in 

 that portion of the cord connected with the galvanometer, then these nerve impulses 

 themselves must be for the most part confined to that side of the cord which they 

 enter. Further, if we assume that the readings furnish us with data for a quanti- ' 

 tative comparison of the amounts of the variously awakened physiological activities 

 on the two sides of the cord, and thus of the number or intensity of the afferent 

 nerve impulses, then this preliminary set of observations would seem to indicate 

 that from four to five times as great a volume of excitatory change flows up the cord 

 on the side of entry of the nerves as on the other. 



This result is fully in accordance with the anatomical evidence previously referred 

 to, and with the results of spread obtained in the cord by excitation of its own 

 columns detailed in Chapter VIII. It is in absolute opposition with the before 

 mentioned results of MIESCHER and WOBOSCHILOFF. 



The indications of these experiments are confirmed by a large amount of collateral 

 evidence dependent upon the influence of section of the various columns. This will be 

 seen as we detail in succession the results of our different lesions. 



Previous Hemiseclion. 



In order to ascertain whether this loss on the side of the lesion was independent of 

 all functional changes due to the shock of the operation, &c., the hemisection was made, 

 in two instances, a considerable time (thirty days and more) before the experimental 

 investigation. 



On the first animal, Cat (283), the hemisection had been made four months pre- 

 viously at the level of the 12th dorsal vertebra on the left side. Before commencing 

 the experiment the animal was carefully examined both in its normal condition and 

 under an anaesthetic. The left hind limb was dragged in walking, and showed 

 marked loss of muscular power. On allowing the feet to touch cold water move- 

 ments were started, the right hind leg being smartly drawn up, the left only after 

 a considerable delay. This and other tests applied to each foot indicated no impair- 

 ment of sensibility on the right side (that opposite to the lesion), but considerable 

 impairment of both tactile sensation and movements on the left, the same side. On 

 placing the animal under an anesthetic the left knee jerk was seen to be much 

 exaggerated, and it was possible to start clonic spasms in this limb. 



For the actual experiment the cord was divided at the level of the 7th dorsal 

 vertebra and the upper end of the lower fragment prepared for connection with the 

 galvanometric electrodes. The electrical effect produced by exciting each of the two 

 prepared sciatic nerves was now observed, the stimulus used being of minimal and 

 maximal intensity respectively and consisting of the usual series of induction currents, 

 100 per second for 5 seconds. 



