228 ANIMAL MECHANICS. 



for the transverse strains. Substituting in succession, the 

 values of ip t and 2p 2 , we obtain — 



Pressure producible by Abdominal Muscles acting at navel, 

 in Parturient Women. 





Deduced from Longi- 



Deduced from Trans- 



No. i. 



17 .59 lbs. sq. in. 



18.13 lbs. f sq. in. 



No. 2. 



19.88 „ „ 



22.84 ,, „ 



No. 3. 





16.09 „ „ 



No. 4. 



11.20 



I5-42 ,» » 



No. 5. 



19 37 „ 



*7-9 6 » »» 



Mean 



16.646 lbs. 



I8.O88 lbs. 



These pressures are produced by the abdominal muscles, act- 

 ing at the navel, under the conditions of curvature, proper to 

 each case ; and are only about half as great as the pressure at 

 navel, obtained by direct experiment (page 163); but they 

 do not represent the maximum pressures producible by the 

 abdominal muscles. In order to show this, let us calculate • 

 the tensile strains produced at each point of the linea alba. 



The longitudinal and transverse strains, produced by the 

 recti and transversalis muscles, are constant at each point of 

 the linea alba ; but this is not the case with the oblique mus- 

 cles. The vertical and horizontal strains of the external oblique 

 are, as shown by equations (38) and (39), 



Tr it COS 0 



V= — x p 



w 



H= t sin 2 <p. 



In these equations, everything is constant except p, the per- 

 pendicular thickness of the portion of the external oblique 



