INDUSTRIAL LABOUR 437 



metre covered was, on the average, 27 small calories, i.e., 

 a. little more than one- third of a small calorie per kilogramme 

 per metre. The expenditure of energy in riding a bicycle 

 is therefore less than in walking. In longer rides at moderate 

 speeds the above expenditure falJs to -26 small calories, but at a 

 speed of 21 km. per hour it rises to -37 small calories. In general, 

 cycling is about twice as economical as walking. The best 

 results are only to be attained by the use of a machine suited to 

 the rider and the adoption of proper attitudes in riding. Bad 

 attitudes, especially if the rider bends too low over the handle 

 bars, cause rapid fatigue. ( l ) From his calculations of the work 

 done and the expenditure of energy Leo Zuntz deduced a yield 

 of 33%. 



The comparatively high efficiency of the bicycle as a means of 

 locomotion is due to the fact that it enables the powerful muscles 

 of the lower limbs to be adequately utilised, while the fractional 

 resistances of the machine itself are but small. 



332. In many industrial machines, such as the grindstone or 

 the foot lathe, the legs are utilised to effect the rotation of the 

 apparatus. The motion of the foot is periodic, and its speed 

 depends on the construction of the machine and the nature of 

 the work being done. It will be observed that a knife grinder 

 varies the speed considerably according to the nature of the work 

 in hand and the pressure which it is necessary to exert on the 

 revolving stone. 



333. Miscellaneous Operations. Typewriting 1 . Most of the 



occupations which have been considered above require a con- 

 siderable expenditure of force. There are, however, others in 

 which the force exerted is but trifling, while the speed is consider- 

 able, such as the operation of the sewing machine, the typewriter, 

 the piano or stringed musical instruments. Speed of execution 

 in such professions and occupations is due to both physiological 

 and physical factors. . Chief amongst the former is the " personal 

 equation " of the subject, a purely individual characteristic, 

 acquired or hereditary. Amongst the latter the flexibility of 

 the joints of wrists, fingers and toes are important, which joints 

 have several degrees of freedom ( 75 and 81). These factors 

 vary widely in different individuals. Apart from the stiffness 

 and clumsiness due to inexperience the rate of reaction of the 

 muscles to excitation varies considerably. 



A distinction should therefore be made between subjects who 

 are physically and physiologically adapted to occupations en- 

 tailing rapid movement, and those who are suitable only for com- 



(*) R. du Bois-Reymond, Berg, and L. Zuntz (Arch. f. Anat. ii. PhysioL, 

 Suppl., 1904, p. 21). 



