436 Mr. J. S. R. Russell. Circumstances under which [May 18, 



History of Previous Experimental WorJc. 



Experimental work directly bearing on the subject commenced 

 •with Schultz and Fiirbringer,* who noted absence of the knee jerk 

 after section of the crural nerve or lumbar roots in rabbits. A like 

 result followed the administration of curara. They also showed that 

 by striking the tendon on one side, under certain circumstances, not 

 only that knee jerk could be elicited, but also that on the oppo- 

 site side. The conclusions come to were that it is not the result of 

 direct irritation of the muscle or its tendon, but a reflex act, the 

 centre for which is situated in the lower part of the cord, and that 

 there can be no question of its being in any sense a cutaneous reflex. 



Tschiriewf excited the divided crural nerve electrically in order to 

 give the muscle tonicity, but never succeeded in obtaining the knee 

 jerk after it had disappeared on section of the nerve. 



Burckhardt,J experimenting on rabbits, concluded that the dura- 

 tion of the phenomenon is less than the time necessary for a 

 cutaneous reflex, that it subsists after section of the posterior roots 

 of the spinal nerves and after destruction of the cord, but that it is 

 abolished by section of the crural nerve ; hence his belief that it is a 

 reflex produced in the spinal ganglia and not in the cord. 



Tschiriew,§ with the knowledge that the crural nerve in the rabbit 

 is formed by the 5th and 6th lumbar roots, divided the cord at the 

 level of the 3rd lumbar, and found that the knee jerk became 

 exaggerated, while when the section was made between the 5th and 

 6th roots the knee jerk disappeared. On making successive sections 

 from the sacral region upwards he found that the knee jerk re- 

 mained intact until the level of the 6th lumbar pair was reached. 

 He divided the posterior roots of the 6th lumbar pair, taking great 

 care not to injure the neighbouring parts, aud found that such sec- 

 tion abolished the knee jerk. Destruction of the segment between 

 the 5th and 6th lumbar pairs resulted in abolition of the knee jerk 

 also. 



Prevost,|| in his first series of experiments, divided the cord in the 

 dorso-lumbar region, whereupon the reflexes below this point became 

 exaggerated. Section of the crural nerve abolished the knee jerk, as 

 did section of the posterior root of the 6th lumbar in the rabbit, 

 while it was augmented when the sciatic alone was divided. These 

 experiments, therefore, confirmed the results of previous observers, 

 especially those of Tschiriew. The next series of experiments were 



* ' Centralbl. f. d. Med. Wiss.,' p. 929, 1875. 



f ' Arch. f. Psych, und Nerv. Krank..' vol. 8, p. 694. 



X Loc. cit. 



§ ' Arch, de Physiol.,' Series II, vol. 6, p. 293, 1879. 



|| ' Rev. Med. de la Suisse Roman de,' February, 1881. 



