METHOD OF TESTING PAIN THE MUSCULAE SENSE. 839 



stimulation occurs in the course of the nerve, or in the centre, or in nerves whose 

 peripheral ends are not accessible, as in the intestines, pain (as belly-ache), which 

 cannot easily be localised, is the result. 



Irradiation. During violent pain there is not unfrequently irradiation of the 

 pain ( 364, 5), whereby localisation is impossible. It is rare for pain to remain 

 continuous and uniform; more generally there are exacerbations and diminutions 

 of the intensity, and sometimes periodic intensification, as in some neuralgias. 



The intensity of the pain depends especially upon the excitability of the sensory 

 nerves. There are considerable individual variations in this respect, some nerves, 

 e.g., the trigeminus and splanchnic, being very sensitive. The larger the number 

 of fibres affected the more severe the pain. The duration is also of importance, in 

 as far as the same stimulation, when long continued, may become unbearable. We 

 speak of piercing, cutting, boring, burning, throbbing, pressing, gnawing, dull, and 

 other kinds of pain, but we are quite unacquainted with the conditions on which 

 such different sensations depend. Painful impressions are abolished by anaesthetics 

 and narcotics, such as ether, chloroform, morphia, &c. ( 364, 5). 



Methods of Testing. To test the cutaneous sensibility, we usually employ the constant or 

 induced electrical current. Determine first the minimum sensibility, i.e., the strength of the 

 current which excites the first trace of sensation, and also the minimum of pain, i.e., the 

 feeblest strength of the current which first causes distinct impressions of pain. The electrodes 

 consist of thin metallic needles, and are placed 1 to 2 cm. apart. 



Pathological. When the excitability of the nerves which administer to painful sensations is 

 increased, a slight touch of the skin, nay, even a breath of cold air, may excite the most violent 

 pain, constituting cutaneous hyperalgia, especially in inflammatory or exanthematic conditions 

 of the skin. The term cutaneous paralgia is applied to certain anomalous, disagreeable, or 

 painful sensations which are frequently referred to the skin itching, creeping, formication, 

 cold, and burning. In cerebro-spinal meningitis, sometimes a prick in the sole of the foot 

 produces a double sensation of pain and a double reflex contraction. Perhaps this condition 

 may be explained by supposing that in a part of the nerve the condition is delayed ( 337, 2). 

 In neuralgia there is severe pain, occurring in paroxysms, with violent exacerbations and pain 

 shooting into other parts (p. 598). Very frequently excessive pain is produced by pressure on 

 the nerve where it makes its exit from a foramen or traverses a fascia. 



VaUeix's Points Douloureux (1841). The skin itself to which the sensory nerve runs, 

 especially at first, may be very sensitive ; and when the neuralgia is of long duration the 

 sensibility may be diminished even to the condition of analgesia (Tiirck); in the latter case there 

 may be pronounced anaesthesia dolorosa (p. 838). 



Diminution or paralysis of the sense of pain (hypalgia and analgia) may be due to affections 

 of the ends of the nerves, or of their course, or central terminations. 



Metalloscopy. In hysterical patients suffering from hemianesthesia, it is found that the 

 feeling of the paralysed side is restored, when small metallic plates or larger pieces of different 

 metals are applied to the affected parts {Burcq, Charcot). At the same time that the affected 

 part recovers its sensibility the opposite limb or side becomes anaesthetic. This condition has 

 been spoken of as transference of sensibility. The phenomenon is not due to galvanic currents 

 developed by the metals ; but it may be, perhaps, explained by the fact that, under physio- 

 logical conditions, and in a healthy person, every increase of the sensibility on one side of 

 the body, produced by the application of warm metallic plates or bandages, is followed by a 

 diminution of the sensibility of the opposite side. Conversely, it is found that when one side 

 of the body is rendered less sensitive by the application of cold plates, the homologous part of 

 the other side becomes more sensitive {Rumpf). 



430. MUSCULAR SENSE. Muscular Sensibility.- The sensory nerves of 

 the muscles ( 292) always convey to us impressions as to the activity or non- 

 activity of these organs, and in the former case, these impressions enable us to 

 judge of the degree of contraction. It also informs us of the amount of the con- 

 traction to be employed to overcome resistance. Obviously, the muscular sense 

 must be largely supported and aided by the sense of pressure, and conversely. 

 E. H. Weber showed, however, that the muscle sense is finer than the pressure 

 sense, as by it we can distinguish weights in the ratio of 39 : 40, while the 

 pressure sense only enables us to distinguish those in the ratio of 29 : 30. In 

 some cases there has been observed total cutaneous insensibility, while the 



