ANIMAL MECHANICS. 



367 



In Fig. 93, the axis LM is drawn at this distance from 

 the vertex 0, and the axis ST is drawn parallel to it, passing 

 through the socket S. 

 Distance between calculated and observed axes = 0.25 in. 



4. Gluteus secundus (a). — This muscle (pyriformis) takes 

 its origin from the under surface of the sacral vertebrae, for a 

 length of 2.60 in., and is inserted into the inner surface of 

 the top of the great trochanter. Its form is shown in Fig. 94, 



Fig. 94. 



where AB and A'B' are its origin and insertion. It is so 

 nearly triangular in shape, that we may safely assume L3f, 

 which bisects the intercept of OX between the bones, to be 

 the axis of maximum effect. ST, as usual, is the axis pass- 

 ing through the observed socket S. 

 Distance between calculated and observed axes = 0.16 in. 



