ioi2 THE MUSCULAR SENSE. 



letting go of the stretched sural triceps often causes reflex contraction 

 of the pretibial muscles. 



Contrary to older observations, 1 it now seems proven that feeble 

 reflexes can be elicited by irritation of joint surfaces, mechanical or 

 thermal. Goldscheider 2 found the effect increase the deeper he 

 penetrated towards the bone. Striking the articular end of a bone 

 elicits reflexes, but these are not truly joint reflexes, for they persist 

 after all the nerves to the end of the bone have been destroyed. 3 So 

 also with periosteal reflexes, they are not truly elicited from the nerve- 

 endings in periosteum. Both these latter sources of reflexes — refl exo- 

 genous regions, as they are sometimes termed — are really dependent on 

 distant bone, to which the mechanical shock is conveyed, and there 

 excites the nerves distributed. Sternberg has obtained reflex contrac- 

 tion of the pretibial muscles (in rabbit) by tapping the bared or lower- 

 cut surface of the tibia, after the lower part of that bone has been 

 severed from the upper by exsection of a piece from the shaft. 



In other experiments, direct excitation of the proximal ends of the 

 nerves of muscles, etc., has been employed. Vasomotor reflexes have 

 been observed to result. In the cat, as I have shown, 4 the excitation 

 of the proximal end of the cut nerve trunk of the group of hamstring 

 muscles — a nerve trunk of exclusively muscular distribution — reflexly 

 affects the innervation of the antagonistic vastus and crureus to the 

 extent of temporarily abolishing the knee-jerk dependent on the 

 spinal tonus of those muscles. Similarly, 5 excitation of the same 

 nerve trunk causes reflex inhibition of the rigid spasm of the extensor 

 cruris, occurring under " decerebrate rigidity." Stimulation of the central 

 end of a twig of this nerve trunk, the rest of the trunk being uncut, 

 produces reflex contraction of the remainder of the hamstring group, 

 and reflex relaxation of the already contracted antagonistic group, the 

 extensors of the knee. 



This is a result comparable with that seen in the self-regulative innervation 

 of the respiratory muscles, 6 and with that given by the afferent nerve of the 

 heart muscle, which inhibits reflexly the constrictors of the arterioles, i.e. the 

 antagonistic muscle. The depressor nerve stands in some respects as prototype 

 of the sensory nerves of all muscle. The vasomotor reflex, following excitation 

 of a muscle by kneading, is said to be invariably lowering of general arterial 

 blood pressure. 7 Certainly that result does often ensue, but not invariably on 

 exciting directly the nerve of a muscle electrically ; I have then seen the blood 

 pressure rise as frequently as fall. Alteration of pulse frequence is noted 

 among the effects, 8 the frequency is at first lessened (through the vagus centre), 

 and later increased (through the nervus accelerans). 9 It is easy to affect 

 respiratory rhythm by excitation of the central ends of muscular nerves. 



That the nerves of muscle are competent to produce pain, is proved by the pain 

 of muscular cramp and other facts. Attempts to assign the pain to the dragging 

 upon or the compression of nerve trunks coursing through or on or between 

 muscles, or to their stimulation by " action currents " of muscles, fail for obvious 

 reasons. It is difficult to satisfy one's self that such reflex effects as these, vaso- 



1 Haller and his pupils, Bichat, etc. - Arch./. Physiol., Leipzig, 1890, S. 380. 



^Sternberg, " Sehnenreflexe," Wien, 1893. 



4 Proc. Roy. Soc. London, 1893, vol. lii. ■> Ibid., 1896, vol. lix. 



6 S. J. Meltzer, Arch. f. Physiol., Leipzig, 1883, S. 209; New York Med. Journ., 

 May 1899. * 6 



7 Kleen, Skandin. Arch. f. Physiol., Leipzig, 1890, Bd. i. S. 247. 



8 Asp, Per. d. k. sacks. Gesellsch. d. Wisscnsch., Leipzig, 1867. 

 "Jacob, Arch. f. Physiol., Leipzig, 1893. 



