1870.] Muscular Forces employed in Parturition. 



261 



Number. 



Diameter of 

 longitudinal curvature. 



Diameter of 

 transverse curvature. 





in. 



in. 



J. Gr. H 



2203 



12-30 



H. 0 



22-73 



12-80 



S. H 



22-52 



12-80 





22-727 



12-633 



The curvature of the distended belly at the navel is found to be, from 

 the foregoing measurements, 



L + L= 1 ,_L_ = _L_. 



Pl p 2 11-3635 r 6-3166 4*0596 



Multiplying this curvature into the tension of the abdominal muscles at 

 the navel already found, viz. 133*67 lbs. per inch, we obtain, finally, 



P= 1^^=32-926 lbs. per square inch. 

 4-0596 r * 



This amount of expulsive force per square inch is available, although 

 not usually employed, to assist the uterus in completing the second stage 

 of labour. If we suppose it applied to the surface of a circle A\ inches in 

 diameter (the usual width of the pelvic canal), we find that it is equivalent 

 to 523*65 lbs. pressure. 



Adding together the combined forces of the voluntary and involuntary 

 muscles, we find — 



Involuntary muscles . = 54*106 lbs. 



Voluntary muscles =523*65 „ 



Total 577'75 „ 



Thus we see that, on an emergency, somewhat more than a quarter of a 

 ton pressure can be brought to bear upon a refractory child that refuses to 

 come into the world in the usual manner*. 



In order to determine by actual experiment the expulsive force of the 

 abdominal muscles, I placed two men, of 48 and 2 1 years of age respec- 

 tively, lying on a table upon their backs, and put a disk measuring 1*87 

 inch diameter just over the navel ; weights were placed upon this disk and 

 gradually increased until the extreme limit of weight that could be lifted 

 with safety was reached ; this limit was found to be in both cases 113 lbs. 

 As the circle whose diameter is 1*8/ inch has an area of 2*937 square 



* The preceding result will no doubt remind the curious and well-informed reade r 

 of the statement made by Mr. Shandy, on the authority of Lithopasdus Senonensis, 1 De 

 partu difficili,' that the force of the woman's efforts in strong labour pains is equal upon 

 an average to the weight of 470 lbs. avoirdupois actiDg perpendicularly upon the ver- 

 tex of the head of the child. 



