ANIMAL MECHANICS. 



Hence there is 10 per cent, of Work lost, in the pectoral 

 muscle, by means of the fan-shaped arrangement of its 

 fibres. 



The temporal 

 muscle in man, 

 shown in Fig. 36, 

 is a remarkable 

 example of fan- 

 shaped muscle ; 

 and there must be 

 a considerable loss 

 of work occasioned 

 by its shape ; this 

 loss of work would 

 be very difficult, 

 however, to calculate, in consequence of the elliptical form 

 of the line of origin of the fibres. 



The latissimus dorsi in man maybe considered as a muscle 

 whose fibres take origin from an arc of a circle, whose centre 

 is the point of insertion in the arm bone ; the mean angle 

 contained by the extreme fibres is 35 0 — hence we find, from 

 equation (33), 



Work done sin 9 3007 

 Inherent Work 0 3°54 



This shows a loss of only 2 per cent., caused by the fan-shaped 

 arrangement of the fibres, whereas the pectoral muscle loses 

 10 per cent., inconsequence of the greater angle contained 

 between its extreme fibres. 



The radiating fibres of the muscle of the iris give us an 

 example of the maximum loss of Work caused by fan-shaped 

 arrangement. We have seen that when the angle between 

 the extreme fibres increases from 35 0 to 90 0 , the loss of Work 



Fig. 36. 



