ANIMAL MECHANICS. 



155 



Mean thickness of muscular wall of uterus, 

 1.56 x 7000 x 1000 



0.15 1 9 inch. 



252.5 x 270.66 x 1052 



If we suppose a ribbon, one inch in width, to be formed 

 from the wall of the uterus, its thickness will be 0.15 19 inch; 

 and as each square inch of cross section of muscular fibre 

 (p. 69) is capable of lifting 102.55 lbs., we find for the greatest 

 tensile force producible by the contraction of the uterine 

 muscles. 



Tensile strain of uterine wall per inch = 102.55 x 0.1519 = 15.577 lbs. 

 Substituting this value of T, in the equation (20) 



9 



and for p, its mean value 9.158 in., we obtain the maximum 

 hydrostatical pressure inside the gravid uterus, that can be 

 produced by the contraction of its muscular fibres. 



Maximum hydrostatical pressure produced by uterine contraction 

 2 x 15.577 



One hundred experiments were made by Duncan and 

 Tait, upon the hydrostatical pressure necessary to rupture the 

 membranes which contain the liquor amnii, which are re- 

 corded in Dr. Duncan's book* (pp. 306-311). The greatest 

 pressure observed was 3.10 lbs., and the least was 0.26 lb. ; 

 and I find that the mean rupturing pressure of all their ex- 

 periments was 1-2048 lb. 



Combining this experimental result with the calculation 

 already given, of the amount of pressure producible by the 

 muscular tissue of the womb, we may conclude that the uterine 

 muscles are capable of rupturing the membranes in every 



*. " Researches in Obstetrics." Edinburgh: 1868. 



