ANIMAL MECHANICS. 



157 



ing resistance (as happens frequently in other cases), ana its 

 precise degree of strength cannot be produced by a tentative 

 process ; for, in healthy gestation, the uterine muscle never 

 tries its force against the membranes it is called upon to rup- 

 ture, until the actual period of parturition has arrived. We 

 witness, therefore, the instructive spectacle of a growing force 

 intended to overcome, at a definite future period, a definite 

 resistance, against which it never measures its strength until 

 the actual moment of conflict has arrived. 



The mind must be singularly constituted, which fails to 

 see in such an arrangement the clear evidence of a Divine 

 Contriver, adapting means to an end, foreseen by Himself. 



The extreme force of uterine contraction produces a pres- 

 sure of 3.402 lbs. per square inch, which is equivalent to a 

 pressure of 54.106 lbs. acting upon a circle of four and a 

 half inches in diameter, which is assumed as the average area 

 of the pelvic canal. 



The maximum force used to expel the foetus, by both ute- 

 rine and abdominal muscles combined, is estimated by Joulin,* 

 from forceps experiments made on the dead body, at 

 1 10.23 ^8., a resu ^ which is regarded by Dr. Duncanj as too 

 large. Dr. Duncan himself considers 80 lbs. as the maximum 

 force ever employed in difficult cases. This would correspond 

 with an hydrostatical pressure inside the uterus of 5.03 lbs. 

 per square inch, which is greater than the uterine muscles, 

 unaided, are capable of producing. 



Dr. Duncan's experiments on the strength of the uterine 

 wall itself show that an hydrostatical pressure of from 17 to 25 

 lbs per square inch is necessary to its rupture ; a result which 

 conclusively demonstrates, when taken in conjunction with 



* " Traite complet des Acconcheraents," p. 447. 

 f " Researches in Obstetrics," p. 323. 



