BROWN- SEQUARD ON THE CENTRAL NERYOUS SYSTEM. 271 



freely admit that attempts to expose this organ either in living or 

 dead animals are surrounded with difficulties, which embarrass the 

 experimenter, and weaken the force of his inferences. The depth at 

 which the spinal cord is situated in most vertebrate animals, its 

 extreme excitability, the intimate connections of its various parts with 

 one another, so that one can scarcely be irritated without the others 

 being affected, the proximity of the roots of its nerves to each other, 

 the difficulty of stimulating one portion of the cord itself without 

 affecting either the anterior or posterior roots, are great impediments 

 to accurate experiments : and when we consider these difficulties, we 

 see a sufficient explanation of the discrepancies which are apparent in 

 the recorded results of experiments, undertaken by so many able 

 observers. 



But these difficulties, great though they unquestionably are, are not 

 insurmountable ; they reflect, indeed, great honour upon him who has 

 done so much to overcome them, but they also teach how slow we 

 ought to be in admitting proofs upon this subject, drawn from experi- 

 mental sources ; and with what caution and care we should examine 

 the tests to which such experimental enquiries have been submitted, 

 before we can accord to their results, as stated by any investigator, 

 our sanction and belief. The tests to which the fundamental ex- 

 periments of Dr. Brown- Sequard have been submitted have been 

 of the most trying nature ; his ideas as to the channels through which 

 sensitive impressions and motive commands pass, came before a scep- 

 tical public, saturated with very different notions, and his experiments 

 have been repeated before large audiences of such persons at various 

 places in these islands. The more sceptical of Iris hearers (ourselves 

 among the number) have made careful autopsies of the animals upon 

 which he had operated, previously hardening the spinal cords in spirit ; 

 and not a few have, like ourselves, repeated his experiments with 

 success. Physiologists whose theoretic views do not harmonize with 

 those of Dr. Brown- Sequard, and who therefore, may have been pre- 

 sumed to have undertaken them in a critical, if not an antagonistic, 

 spirit, have had the candour to confess that their ideas have been 

 modified by a repetition of these experiments : # and, moreover, his 

 principal assertions and experiments have passed with approval, through 

 the severe ordeal of a commission, appointed by the Societe de Biologic, 

 and composed of MM. CI. Bernard, Bouley, P. Broca, Griraldes, 

 G-oubaux, and Yulpian. At page 42 of his lectures Dr. Brown- 

 Sequard himself observes in a note, 



" I must say, that it is absolutely impossible to know, while we make a section 

 of parts of the spinal cord, what is the precise depth of the injury; it is mere guess 

 work. But if we study well the phenomena, and then after having killed the animal, 

 if Ave put the spinal cord in alcohol, we render it hard, and we can ascertain exactly 



* Compare Schroeder van der Kolk, On the minute structure and functions of 

 the spinal cord — translated from the original. Sydenham Society, 1859, page 

 51, note. 



YOL. I. — N. H. R. 2 N 



