936 THE MUSCULAR SENSE. POWER-SENSE. 



designation cutaneous paralgia may be applied to certain unpleasant or painful 

 abnormalities of sensation that are frequently localized in the skin, namely 

 itching, formication, ^burning, and cold. In cases of cerebrospinal meningitis 

 a prick on the sole of the foot has occasionally been observed to cause a double 

 sensation of pain and a double reflex contraction. Perhaps this phenomenon may 

 be explained by supposing that the conduction is delayed in a part of the irritated 

 nerve. Neuralgia occurs in the form of characteristic paroxysms of pain of great 

 violence, with radiation elsewhere (for example neuralgia of the fifth nerve, p. 

 692). It is due to pathological processes in the nervous apparatus. Frequently 

 during the attacks excessive pain is produced by pressure on the points where the 

 nerve-trunks emerge from the bony canals or openings in the fasciae, or grooves 

 (Valleix' points douloureux). The skin itself to which the sensory nerve passes 

 may, especially at first, be the seat of great sensitiveness, but if the neuralgia be 

 of long duration, the sensibility may be much impaired, up to the point of analgesia. 

 In the latter event there may be pronounced painful anesthesia. 



Diminution or abolition of the sense of pain (hypalgia and analgia) may be 

 due to affections of the nerve -terminations, or of the nerve- trunks, or of the central 

 insertions of the nerves. 



In hysterical subjects, suffering from hemianesthesia, the remarkable ob- 

 servation has been made that the feeling of the affected side is restored when small 

 metallic plates or compresses are applied to the skin (metalloscopy) . At the same 

 time that the affected part recovers its sensibility, the corresponding part of the 

 opposite, healthy side or limb becomes anesthetic. It has been thought that 

 a transference of sensibility takes place from the healthy to the affected side of 

 the body. The application of the metallic plates gives rise to galvanic currents 

 whose intensity varies with the character of the metal, but the resulting phenom- 

 ena cannot be attributed to these currents. The explanation of the fact is found 

 in the circumstance that a similar result occurs under entirely normal, physio- 

 logical conditions. In a, "healthy person every increase in sensibility on one side 

 of the body, produced by the application of warm metallic plates or compresses, 

 is followed by a diminution in sensibility on the opposite side. Conversely, it 

 is found that when one side of the body is made less sensitive by the application 

 of cold metallic plates, the homologous part of the other side becomes more sen- 

 sitive. 



THE MUSCULAR SENSE. POWER-SENSE. 



The sensory nerves of the muscles constantly convey impressions 

 as to the inactivity or activity of the muscles, and in the latter event, 

 as to the degree of contraction (power of distinguishing the weights 

 of various objects). They furnish information also as to the amount of 

 the contraction to be employed to overcome resistance (power-sense). 

 The power of differentiating the weight of objects lifted is based upon 

 a comparison of the degree of innervation with the duration of the 

 latent period, that is of the time that elapses between the willing of 

 the movement to raise the object and the actual commencement of 

 the movement. In a. wider sense the muscular sense includes also the 

 appreciation of active and passive movements, the recognition of posi- 

 tion, and finally that of resistance and weight. Obviously, the muscular 

 sense must be largely aided by the pressure-sense, and conversely; 

 although E. H. Weber showed that the muscular sense exceeds the 

 pressure-sense in delicacy, as by its aid weights in the ratio of 39 : 40 

 can be distinguished, while with the aid of the pressure-sense only those 

 in the ratio of 29 : 30 can be distinguished. In some cases in man 

 perfectly retained muscular sense has been observed in conjunction 

 with total cutaneous insensibility. A parallel condition is the ability 

 of a frog deprived of the skin on its legs to jump without material 

 disturbance. The muscular sense is also greatly aided by the sensibility 

 of the joints, the bones, the fascias and the tendons. By the associated 

 action of several sensations, especially in the muscles and tendons, 



