PHYSIOLOGICAL EFFECTS OF LABOUR. 211 



There is, as already stated, a tendency, with most physiologists, 

 to carry the seat of fatigue into the extreme points of the nervo- 

 motor filaments, but the medullary centres seem more likely 

 than the preceding, as, after a tiring period of work, a sensation 

 of resistance which lasts for several hours is experienced. 



During work lasting seveial days, the daily maximum is reached 

 by the workmen who can the best resist discomfort, because the 

 sensation of pain is often mingled with the sensation of fatigue. 

 A sort of blunted sensibility protects men in certain occupations 

 from the moie or less painful efforts that they exert. To get an 

 idea of a subject's resistance to fatigue, we should consider the 

 sum of the work done or the expenditure of energy each day, 

 rather than the static effort Ft. Neither the static nor the 

 dynamic idea of endurance apply in a state of extreme fatigue or 

 overwork, which springs from physiological causes and denotes 

 bad organisation. 



149. Nervous Fatigue : Intellectual Activity. The activity of 

 the muscles give rise to an expenditure of energy which is 

 measurable in calories and an equivalent consumption of oxygen. 

 The activity of the nerves is more obscure. 



However, since there is a respiratory action in nervous matter, 

 as in all tissues, Thunburg, of Lind, invented a little instrument, 

 the microrespirometer, by means of which he found that the fila- 

 ments of the nerves consume in pure air, at a temperature of 

 20 C., 22-20 cubic millimetres of oxygen per gramme per hour, 

 and exhale 22 cubic millimetres of carbonic gas.( J ) These ex- 

 changes of gas are a little more active when the tissue is in its 

 place" in the" living animal. ( a ) surrounded by nourishing liquids. 

 Even allowing a double expenditure of oxygen, 45 cubic milli- 

 metres per gramme-hour, it would be found that for the 1,700 

 grammes that the nervous mass of an adult represents, and in 

 24 hours : 



0-045 c.c. X 1,700 X 24 = 1,836 cubic centimetres, 

 equals : 1,838 X 5-05 Cal. = 9-27 Cal. 



This calorific production is about T^O of that of the entire 

 organism taken in repose. It will be understood that no appreci- 

 able rise of temperature of the brain 01 of the nerves can be de- 

 tected when they are excited electrically. ( 3 ) 



(*) Thunberg (Centralblatt /. PhysioL, vol. xviii., p. 553, 1905), experiment 

 on the brain of a dog ; Batelli and Stern obtained higher values (Journ. 

 de Physiol., 1907). 



( a ) A. Waller, Lecons sur I'Electricitt Ammale). 



( 8 ) De Boeck, Thise de Bruxelles, 1893 ; Cremer (Sitzungsb. d. Gesellsch. 

 f. Morph. u. Physiol. zu. Miinchen, 1896) ; A. Mosso (Arch. ItciL Biol., 

 yols. xviii. and xxii). 



