ANIMAL MECHANICS. 



161 



abdominal muscles along the curved central line of the 

 belly. 



There remain now to be ascertained the principal curva- 

 tures of the abdominal surface, and to use the equation, (19) 



so as to determine P, the hydrostatical pressure per square 

 inch inside the cavity of the- belly, and available, either in 

 whole or in part, for the expulsion of the foetus during the 

 second stage of labour. 



In order to ascertain the curvature of the belly, I made 

 experiments upon three young men, placed lying upon their 

 backs upon the floor, and made them depress and raise the 

 abdominal wall as much as possible. The result was as fol- 

 lows : — Taking a straight line from the upper part of the sym- 

 physis pubis to the xiphoid cartilage as the fixed line of com- 

 parison, it was found possible to depress the navel one inch 

 below this fixed line, and to raise it two inches above it. 

 When the belly was distended to the utmost, by the action of 

 the abdominal muscles, I measured the longitudinal and trans- 

 verse curvatures, by measuring the sagittas corresponding to 

 a given length of tangent, with the following results : — 



No. 



Diameter of Longitudinal 

 Curvature. 



Diameter of Transverse 

 Curvature. 



J. G. EL, . . 

 S. EL, . . . 



22.93 inches. 



22-73 » 

 22.52 „ 



1 2 . 30 inches. 

 12.80 „ 

 12.80 „ 



Mean, . . 



22-727 inches. 



12-633 inches. 



M 



