568 DISEASES OF THE ORGANS OF LOCOMOTION. 



cular atrophy is a gradually increasing feeling of weakness in certain 

 muscles or groups of muscles, with their very evident and steadily 

 increasing emaciation, but without pain or other trouble. The dis- 

 ease does not originate with equal frequency in the different mus- 

 cles ; but, in most cases, the muscles of one hand or one shoulder 

 are first affected, occasionally those of the neck, rarely those of the 

 face. The power of conduction and the size of the muscle, which 

 diminish about equally in the course of the disease, are finally so 

 much reduced, that the movements depending on the affected mus- 

 cles are entirely lost or very imperfectly made, and, where the belly 

 of the muscle was formerly prominent, we find a flatness or even a 

 depression. The effect induced is most apparent in the disappear- 

 ance of the ball of the thumb, depressions between the metacarpal 

 bones, flattening of the shoulder, and prominence of the spinous 

 processes of the vertebrae, when the muscles of the neck have atro- 

 phied. In the weak and atrophied muscles we may always see a 

 peculiar fibrillar twitching that has no effect on the point of inser- 

 tion of the muscles, and hence induces no movement of the corre- 

 sponding joint ; this twitching becomes more evident when we blow 

 on the skin covering the muscle, or irritate it in any other way by 

 exposure to cold. It is usually said that the excitability of the sen- 

 sory cutaneous nerves remains normal, and only that of the sensory 

 muscular nerves is lost (the "electro-muscular sensibility" of the 

 electricians) ; but I have seen many cases where the excitability of 

 the cutaneous nerves was much diminished, while all the other 

 symptoms were those of progressive muscular atrophy. A very im- 

 portant and even pathognomonic symptom is the above-mentioned 

 condition of the affected muscles and their motor-nerves in regard 

 to the induced current ; this current does not fail to induce con- 

 traction until the muscle is entirely atrophied ; up to that time the 

 contractions correspond to the strength of the current and the 

 amount of muscular substance that still remains. In some cases 

 progressive muscular atrophy is limited to certain parts of the 

 body ; in others it gradually extends to the greater part of the 

 muscles supplied by the cerebro-spinal nerves, while it never affects 

 the muscles of the heart, intestines, or bladder. The latter form is 

 a terrible disease ; patients affected with it preserve a good appetite 

 and good digestion, their intellect is clear, and the mental functions 

 are so unclouded that they can fully comprehend their lamentable 

 loss, while they lose the use of one limb after another. In advanced 

 cases the patients cannot walk or change their position ; they must 

 be fed too, as their arms hang useless by their sides ; the changes 

 of expression cease, the saliva runs out of the mouth, the speech is 



