322 



THE HUMAN MOTOR 



1. The skin, being well stretched, is touched with a metal 

 point. The subject then indicates the point touched. The 

 capacity of localisation is then inversely proportional to the 

 distance in millimetres between the actual point of contact and 

 that indicated by the subject. 



2. By Weber's esthesiometer. This consists of a caliper gauge 

 with pointed arms, which are applied slightly and simultaneously 

 to the skin. 



Fio. 229. 



The degree of sensibility is given by the smallest distance 

 between the points at which they are both distinctly felt (fig. 

 229). 



Various types of esthesiometers are used at the present time. 

 The localising capacity is highly developed in the blind, and is 

 greater in children than in adults, vide the following table, due 

 in part to Weber ( 1 ). 



ADULTS 



Tip of the tongue 1TO mm. 



, ; nose 6-80 



Palm of the hand 8-90 



Eyelids 11-30 



Back of the hand 31-60 



Sternum 45-10 



Middle of the back, arms, and thighs 67-70 



CHILDREN 



1-10 mm. 

 4-50 







9-00 



22-60 



33-80 



40-60 



250. Measurement of the Thermal Energy of the Body. The 



exact measurement of the thermal expenditure would necessitate 

 an expensive installation, such as Atwater and Benedict's calori- 

 metric chamber, d' Arson val's calorimeters, etc., for which the 

 reader must be referred to the original memoirs. ( 2 ) 



Thermal energy comprises the energy of physical waste and 

 that of the physiological minimum. The waste is calculated 

 from the theoretical relations of the radiation and of the convec- 

 tion in the air at an external temperature of t ( 165) . If Newton's 

 law is applied Kj will be taken as equal to 0.00015c for the 

 emissive power. If Stefan's law is used ( 171) K' x will be taken 

 as 1-02 X 10' 12 in the formula : 



g 1 = K/ 1 [(T + 273) 4 (t + 273)*]. 



C) Consult Victor Henri (Arch, de PhysioL, 1893, pp. 619-27) ; Marillier 

 et Philippe (Journal de PhysioL, 1903, p. 65). 



(*) Jules Lefevre, in his Bio inevg Clique (loc. cit., pp. 77 sqg.} gives a 

 complete and methodical study of the subject. 



