BROWN- SEQTT ART) ON THE CENTRAL NERYOTTS SYSTEM. 405 



time been before the scientific public, in Dr. Brown-Sequard's " Ex- 

 perimental and Clinical Kesearches on the Physiology and Pathology 

 of the Spinal Cord," published in 1855. 



In a notice like the present, it would be quite impossible to 

 deal with the many secondary questions which are touched upon in 

 Dr. Brown-Sequard's eminently suggestive work. There are, how- 

 ever, two of these which we cannot refrain from mentioning : 1st, 

 as to the muscular sense, i. e. the appreciation of the feeling which 

 accompanies muscular contraction, and which, in its exaggerated con- 

 dition, constitutes the excruciating suffering which attends cramp 

 and various muscular spasms ; and 2ndly, as to the hyperesthesia 

 which follows the section of a lateral half of the spinal cord in the 

 posterior limb, on the same side as the lesion. 



Magendie discovered, in 1839, that irritation of the anterior or 

 motor roots of the spinal nerves causes pain, and further, that when 

 these roots are divided, irritation of the distal extremity only gives 

 pain ; while if the posterior roots of the corresponding spinal nerves 

 be next cut across, pain no longer results from the irritation just 

 mentioned. On these facts Magendie founded his hypothesis of re- 

 current sensibility. Now what may be the cause of the pain result- 

 ing from an irritation propagated, thus centrifugally along a motor, 

 and then centripetally along a sensitive nerve ? To this question 

 Dr. Brown- Sequard gives a most ingenious answer. Although 

 Matteucci and Dubois Eeymond differ as to the explanation of the 

 phenomena, yet all agree that if a so-called rheoscopic frog's leg be pre- 

 pared and laid on an insulating plate, and a second leg be laid across 

 it, so that the nerve alone of the second is in contact with the muscles 

 of the first, a contraction produced in the first leg, by galvanic or other 

 stimulus, is followed by a secondary (or induced ?) contraction in the 

 second, and so for three or four limbs under favourable circumstances. 

 This is due to some change in the galvanic state of the muscle, 

 which by its contraction thus excites the nerve lying on it. Now 

 Dr. Brown-Sequard supposes that this change in the galvanic state 

 of a muscle is, in the natural condition, perceived by the sensitive 

 nerves of the muscle ; and the delicate perception of this galvanic 

 change accompanying muscular contraction, however slight, gives to 

 us a correspondingly delicate appreciation of the feeling of weight, 

 which is one of the most striking phases of the so-called " muscular 

 sense." The more violent the contraction, the more marked is the 

 disturbance of the galvanic equilibrium, and consequently the more 

 distinct and strong the impression conveyed to the central nervous 

 system. Normally these contractions are unaccompanied by pain, but 

 if the muscular contraction be very violent, or if the centripetal 

 nerves of muscle be in a hypersesthetic condition, pain results, and 

 hence that accompanying spasm and cramp. In support of this 

 view Dr. Brown- Sequard gives the following experiment : 



11 If we fix a thread to the tendon of a muscle of a frog and attach to this 

 thread a weight, capable of entirely preventing the contraction of the muscle, 



