192 



ANIMAL MECHANICS. 



done increases from 2 to 10 per cent. When the fibres 

 radiate through a semicircle, we have 

 Work done sin 0 2 

 Inherent Work 0 it 

 This corresponds to a loss of nearly 36 per cent. 



Deltoidal Muscles, — The deltoid figure of geometers is a 

 quadrilateral figure, formed by constructing two isosceles tri- 

 angles, with unequal vertical angles upon the opposite sides of 

 the same base. 



Deltoidal muscles are found in nature, formed by the union 

 of two triangular muscles. 



An excellent example is to be found in the trapezius 

 muscle of man, shown in Fig. 37. 



X 



Y 



The whole figure XAYB is a deltoid, and is formed by 

 the union of the two triangular muscles X^I^and XBY; the 



