THE TEMPERATURE-SENSE. 



931 



between which points of another sensation are frequently interposed. 

 In this way mixed punctate chains arise. Near hairs there are almost 

 always temperature -points ; in areas of the skin with feeble temperature- 

 sensibility, the temperature -points are present only near the hairs. 

 According to Abrutz the cold-points are situated more superficially in 

 the skin than the heat-points; according to v. Frey, Krause's bulbs are 

 the organs for the perception of cold, the nerve -plexus that for the 

 perception of heat. 



The heat-points are larger than the cold-points ; the slightest mechani- 

 cal irritation of the latter excites a sensation of cold. The cold-points 

 react to feebler e'ectrical stimuli than do the heat-points; chemical 

 irritants also are capable of exciting the heat-points. The feeling of 

 cold occurs at once, that of heat appears gradually. 



A gentle touch is not perceived as such at the temperature -points, 

 which seem to be anesthetic for pressure and pain. In general, the cold- 

 points preponderate upon the entire body, and they are denser, while 

 in many places the heat-points are entirely wanting. With regard to 

 the degree of sensibility the points may be divided into those that are 



C.P. 



W.P. 



B 



c 



D 



FIG. 343- A Cold-points; B heat-points on the palmar aspect of the distal phalanx of the index-finger to the margin 

 of the nail (Goldscheider). C, Cold-points and D heat-points on the radial half of the dorsal aspect of the 

 wrist (the arrow indicates the direction in which the hair points (Goldscheider). 



extremely sensitive, those that are moderately so, those that are slightly 

 so, and those not at all sensitive. It is possible to indicate the intensity 

 of the temperature-stimulus and the point where it is applied. The 

 heat-points are, on an average, perceived as double at greater distances 

 than the cold-points. The minimal distances upon the forehead are 

 for the cold-points 0.8 mm., for the heat-points from 4 to 5 mm., on the 

 chest the respective values are 2 and from 4 to 5 mm., on the back 

 from 1.5 to 2, and from 4 to 6, on the back of the hand from 2 to 3 and 

 from 3 to 5, on the palm of the hand 0.8 and 2, on the thigh and leg 

 from 2 to 3, and from 3 to 4 mm. 



For testing the heat-points and the cold-points a pencil-shaped 

 metallic rod heated to from 45 to 49, or cooled to 15, is employed. 

 When the cold-points are lightly touched only the cold rod is felt and 

 as cold; and only heat is appreciated by the heat -points. Both kinds 

 of points are insensitive to lightly applied objects of the same tempera- 

 ture as the skin. 



The determining factor with respect to temperature-sensibility is, 

 according to E. Hering, the temperature of the thermal end-organ itself. 

 Whenever the temperature of the latter in any part of the cutaneous 

 surface is above its own zero-tempefature, that is, its normal temperature, 



