404 A MANUAL OF VETERINARY PHYSIOLOGY 



emphasises the ill-effects of straining the tired machine. The 

 effect of hunger, want of rest, mental activity, is found to diminish 

 the amount of work produced. When the circulation in the muscle 

 is improved by massage, more work is produced. The effect of 

 improving its nutrition by food, especially by a readily soluble 

 and easily absorbed substance such as sugar, is said to increase quickly 

 its power of performing work. Finally, the effect of making a 

 prolonged call for work upon one group of muscles is to diminish 

 the activity of the others. The results obtained by the ergograph 

 are those which accord with experience, but it is unfortunate that 

 the personal element cannot be excluded from the experiments, 

 especially where the questions of food and work are concerned. 



Fig. 120. — The Ergograph (Mosso's). 



In connection with the work done by muscle, it is interesting to 

 institute a comparison between the work yielded by the animal 

 body and that by a well-constructed machine. The best triple- 

 expansion engine may yield as work some 10 to 15 per cent, of 

 the available energy in the fuel, the balance is lost as heat ; in 

 other words, the ' efficiency' — that is, the fraction of the heat it 

 receives which it converts into work — of a good engine is ^ to ^. 

 In the animal body various statements have been made as to the 

 proportion of work done to the available energy. Chauveau, 

 working with the lip-muscle of the horse, placed the work at 

 12 to 15 per cent, of the energy liberated, the difference being 

 accounted for as heat. If this were the case the muscle machine 

 would seem to be very little more economical than the steam- 

 engine. Now, Fick showed, some thirty years ago, that the 

 efficiency of an excised muscle of the cold-blooded frog may be 

 as much as J or even J, and we may not unreasonably expect that 

 mammalian muscle, in the body with its circulation intact, would 

 be still more efficient. And this is borne out by Zuntz's experi- 



