POWER EXERTED IN THE FUNCTION OF PARTURITION. 



649 



into lbs., as well as increased proportionally from what appertains to a radius of 

 5 centimetres to what appertains to a radius of 2\ inches, the dimensions used in 

 our experiments : — 



1 



No. 



Belastungbei 10 Centi- 

 meter Durchmesser 

 Kilogramm. 



Pressure for Diameter 

 of 2 - 25 inches in lbs. 



1 



3 

 12 

 13 

 22 

 23 

 28 



Kilogrammes. 

 9-876 

 2346 

 2134 

 7608 

 4-709 

 9461 

 7001 



lbs. 

 27232 

 6-469 

 5-884 

 20-979 

 12-985 

 26088 

 19-305 



This table gives us, in seven cases, a figure of strength nearly equalling the 

 whole power of labour in these cases. If, in any of the cases, the membranes 

 had persisted after the birth, then the figure in the last column would have cer- 

 tainly exceeded the whole propelling power of labour at any moment during the 

 whole of the labour. Speaking of them, Poppel remarks, that " if we reflect that 

 the table expresses only the minimum of power for the easiest labours, the figures 

 appear to be quite trustworthy, even though they exhibit great variations. It 

 may therefore be assumed that in a very easy labour a power, varying from 4 to 

 19 lbs., presses the head through the pelvis." As Dr Poppel gives the passage 

 transmitting the head a diameter of 4 inches, and as I prefer regarding it as 

 nearer 4^, so I, using meantime Poppel's experiments and calculations, make the 

 power exerted in an easy labour vary from about 6 lbs. to about 27 lbs., instead 

 of from 4 to 19. I shall not meantime attempt to show whether Poppel's 

 assumed 4-inch diameter or my assumed 4|-inch diameter is the more likely to 

 be nearest the truth, because it would lead me into a class of questions remote 

 from the subject matter of this paper. 



If we observe, that in Poppel's table of experiments and in mine the power 

 shown to be sufficient to terminate an easy labour was often far exceeded in the 

 course of other labours, we may enunciate the almost certain conclusion that a 

 great mass of easy, and not merely of the easiest, labours is terminated by a 

 power little in excess of that required to rupture the bag of membranes. The 

 strongest membrane found in the experiments indicated, by the pressure required 

 to burst it, an extruding force of 37^ lbs. We may therefore, I think, safely 

 venture to assert as a highly probable conclusion, that the great majority of 

 labours are completed by a propelling force not exceeding 40 lbs. 



If we regard the figure of 4 lbs. given by Poppel as equal to the power exerted 

 in the easiest labour he has observed, or the corresponding figure of 6 lbs. 

 according to my calculations, and keep in mind that the average weight of the 



