CUTANEOUS AND INTERNAL SENSATIONS. 259 



peculiar quality of sensation. According to this view, artificial 

 stimulation, if properly controlled, of the trunks of the nerves 

 supplying the skin should be capable of bringing out these different 

 sense qualities. Experiments made with this point in view have 

 not, however, been very successful. Mechanical or electrical stimu- 

 lation of the ulnar nerve, for instance, gives usually only pain sensa- 

 tions, although if the stimulus is feeble contact sensations are 

 aroused. The method, however, is probably at fault. In the case 

 of amputated fingers or limbs a more decisive result is obtained. 

 As is well known, individuals after such operations may for many 

 years have sensations of their lost fingers or limbs. In such cases 

 the pressure in the stump of the wound acting upon the central 

 ends of the sensory fibers arouses sensations which are projected 

 in the usual way, and give the feeling that would be experienced 

 if the lost parts were still there and were stimulated in the normal 

 manner. 



The Temperature Senses. The main facts regarding the 

 distribution of heat and cold spots have been determined. In gen- 

 eral, the cold spots are more numerous than the warm spots, and 

 react more promptly to their adequate stimulus. The cold spots 

 or the cold sense may be present in places devoid of the sense of 

 warmth; thus, it is said that the glans penis possesses only the 

 cold sense. The threshold stimulus varies also in different parts 

 of the skin, the tip of the tongue requiring the smallest stimulus 

 to arouse a sensation, and the eyelids, forehead, cheeks, lips, limbs, 

 and trunk following in the order named. According to Goldscheider, 

 the spots on most portions of the skin form chains that have a some- 

 what radiate arrangement with reference to the hair follicles. The 

 temperature points possess each its adequate stimulus, that for the 

 cold spot being temperatures lower than the skin or of the terminal 

 organ of the cold nerves, that for the heat spots temperatures higher 

 than their own. Apparently, therefore, one end-organ is excited 

 by a diminution in the atomic movements of its organ, and the 

 other by an increase. Nothing is known, however, of the exact 

 nature of the stimulating process. From the standpoint of specific 

 nerve energies it is most interesting to find that these points, particu- 

 larly the cold spots, may be stimulated by other than their adequate 

 stimuli. Mechanical and electrical stimulation has in the hands of 

 several observers been efficient in causing a sensation of cold upon 

 a cold spot and of heat upon a warm spot. Some chemical stimuli 

 are also effective. Menthol applied to the skin gives a cold sensa- 

 tion, while, on the other hand, if the arm be plunged into a jar of 

 carbon-dioxid gas a distinct warm sensation will be experienced. 

 A curious effect of this kind is what is known as the paradoxical cold 

 reaction. It is produced by applying a very warm object, with a 



