ANIMAL MECHANICS. 



221 



Hence, if w denote the width of the recti muscles, and p the 

 length of AK, the vertical component per linear inch will be 



V= p X t X 2 COS 0 , v 



w ^ 



The horizontal strain corresponding to a linear inch of the 

 linea alba will not, of course, be the strain corresponding to a 

 width (AK) of muscle, but is produced by a width equal to 

 sin 0 ; substituting this width for AK, we find 



H= t x sin ? 0. (39) 



I find, by careful measurements, the following values to 

 be substituted in the foregoing expressions — 



AK = 4.25 in. 

 t = 0.25 „ 



0= 35° 

 iv = 5,41 in. 



Hence we obtain, finally, 



V = 4.25 x 0.25 x 2 cos 35 0 



0.321 



5.41 5 



0.25 x sin 2 35 0 = 0.082. 



The internal oblique muscle is shown in Fig. (53), where 

 P, N, 11, denote the pubes, navel, and crest of ilium, and 

 AB the insertion of the muscle into the outer border of the 

 rectus sheath. The internal oblique muscle is not prismatic, 

 but quadrilateral, and its action is more complicated than that 

 of the external oblique. The upper fibres give a vertical com- 

 ponent which draws the linea alba, downwards, towards the 



