ii SENSIBILITY OF THE INTEKNAL OKGANS 99 



graduated action of several muscles. Owing to their simplicity 

 the force, amplitude, and direction of the movements of the 

 joints is readily appreciated ; the simultaneous contraction of 

 several muscles, on the contrary, can arouse no compound resultant 

 sensation unless there is a separate consciousness of the difference 

 in intensity of the single elementary components of the sensation 

 and their associations. 



In the clinical case described by Strlimpell (p. 90, Figs. 36, 37) 

 the loss of the sensations of posture and of active and passive 

 movement in the right hand depended not on paralysis of the 

 muscles and tendons, but on the insensibility of the joints. In 

 fact, in Duchenne's case (p. 90), where there was loss of cutaneous 

 and muscular sensibility in the left upper limb, while articular 

 sensibility persisted, the patient was aware of the posture and of 

 active and passive movement. 



Lewinski (1879) had under observation an ataxic patient who 

 in standing erect and walking felt as if his right knee were turned 

 in (as in genu varum), and was obliged to look to convince him- 

 self that it was straight like the left knee, but when he lay down 

 in the horizontal posture the illusory sensation ceased. As the 

 sensibility of the skin and muscles was the same on both sides of 

 the leg, Lewinski concluded that the anomalous sensation was due 

 to a diminution of sensibility on the inner side of the joint. Under 

 ordinary conditions, the sensation in standing, excited by the 

 weight of the body, is uniformly distributed over the whole surface 

 of the joint ; when sensation is defective or absent on the inner 

 surface the patient feels as if both articular surfaces of the knee 

 were compressed on the outer side, and were not in contact on 

 the inner side, as if the leg were bent outwards, making an angle 

 that opened externally. The anomalous sensation disappears in 

 the horizontal posture because the cutaneous tactile sensations 

 correct the illusion and supplement the defect in articular 

 sensibility. 



Lewinski further saw that if passive movements were executed 

 at different joints on this ataxic patient he only became aware of 

 them when the surfaces of the joints were pressed strongly one 

 against the other. From this he concludes that there is no doubt 

 that sensations of posture depend exclusively on the compression 

 of the two articular surfaces, and sensations of passive movement 

 on the constantly changing points on those surfaces that are com- 

 pressed during the changes in the relation of the articular heads.- 



The important experiments of Goldscheider further support 

 this theory. He caused his limbs to be moved passively, and 

 recorded on an apparatus the speed of the movements and their 

 angular value. He found that in many joints quite small move- 

 ments, frequently less than one degree (072 - 0-22), could be 

 appreciated. 



