ANIMAL MECHANICS. 



223 



the strain per linear inch, as in the case of the external oblique' 

 Hence we find, finally, 



, r 2/'sin 0 x 2 cos (h 2/ versin 20 . . 



V = r = J. . (40) 



to w ' 



In this equation, /is equal to the product of the cross section 

 of the muscle, multiplied by its width enclosed between the 

 lines NX and IF. 



Cross section of internal oblique = 0.17 in. 



Width of do., = 2.97 „ 



e = 9 o° - 0 = i 3 ° 



Width of recti muscles, . . . = 5.41 in. 

 Hence we have 



T7 2 x 0.17 x 2.97 x versin 26 0 



V= — - = 0.010. 



5.41 



The transverse strain produced at the navel by the inter- 

 nal oblique muscle, depends on the direction of the fibres in 

 its neighbourhood only, and is found by the same formula as 

 the transverse strain of the external oblique muscle, viz. — 



H = t x sin 2 0, (41) 



which gives us, for the transverse strain, per linear inch at 

 the navel, 



H = 0.17 x sin 2 64° = 0.137. 

 Adding together the vertical and transverse tensile strains 

 produced by all the muscles at the navel, we find — 



Vertical Tension due to Abdominal Muscles. 



Rectus abdominis, 0.290 



Obliquus externus, °-3 21 



Obliquus internus, 0.019 



Transversalis, 0.000 



0.630 



