98 PHYSIOLOGY CHAP. 



muscles, tendons, and articular tissues has the greatest physio- 

 logical importance in arousing the so-called muscular sensations 

 by which movements are controlled? In this connection some 

 interesting physiological and clinical observations may be cited. 



Certain early observations of Haller and Bichat, confirmed 

 later by Schiff, Bernstein, and others, show that the muscles and 

 tendons are insensitive to many mechanical, thermal, chemical, and 

 electrical stimuli which are effective in other tissues. Sherrington, 

 however, showed that the tendons may be the starting-point of 

 reflexes. Compression of the tendon of the tibialis anticus of the 

 cat invariably produces a reflex in the adductor femoris. Eeflexes 

 can be obtained from other muscles. On pinching the muscles of 

 a curarised rabbit, Kleeii obtained a fall of arterial pressure. Before 

 that, Sachs obtained reflex convulsions in a strychninised frog, by 

 exciting the central stump of a nerve to the sartorius. Sherrington 

 showed that the knee-jerk phenomenon may be reflexly inhibited 

 by compressing or otherwise stimulating one of the leg- 

 muscles. He also saw that the sudden relaxation of a muscle 

 passively pulled on often discharges a reflex in some other muscle : 

 that the direct stimulation of the muscular nerves gives rise to 

 vascular reflexes, often also to alterations of respiratory rhythm ; 

 produces antagonistic effects (by lowering muscle tone) in other 

 groups of muscles ; causes decerebrate rigidity to disappear ; and 

 finally may induce reflex contraction of other muscles. From 

 these facts we may conclude that the more or less appreciable 

 sensations aroused by excitation of the sensory nerve organs of 

 the tendons and muscles are not unimportant to ,the regulation 

 of movements. 



Other facts, however, indicate that the muscular sensations 

 due to excitation of the afferent nerves of the tendons and muscles 

 remain, under normal conditions, almost entirely below the 

 threshold of consciousness, and are only of negligible, certainly 

 only of secondary importance, as factors in the complex sensations 

 that accompany voluntary movements ; and that greater import- 

 ance attaches, on the contrary, to the excitations arising from the 

 afferent nerves of the articular tissues. This theory was maintained 

 by Kauber, Duchenne, and Lewinski, more particularly on the 

 strength of clinical observations, and was more fully developed 

 by Goldscheider (1889) on the basis of accurate experimental 

 research. 



It seems a priori probable that the sensibility of the articular 

 tissues as a whole should be of predominating importance in the 

 genesis of the sensations by which movements are reflexly regulated. 

 Every change in the relations between two articular surfaces 

 corresponds to a simple movement, while there is perhaps no 

 muscle that takes part in a single movement only, nor any move- 

 ment that is not the result of the associated and variouslv 



