376 Proceedings of the Royal Society 
It is well-known to accoucheurs that the great resistance to the 
progress of the child in the second stage of labour is what is called 
in obstetrics the perineum. The power of this part I do not know, 
and guessing is a bad proceeding in a scientific paper. Yet I may 
venture to say that no perineum would long resist a force of 50 
lbs. repeatedly applied, a force less than Haughton ascribes to the 
uterine muscle. 
II. Haughton ’s second conclusion is that the chief force in par- 
turition is furnished by the voluntary muscles. The available 
power of these is (he says) 523 lbs., while that of the uterus is 54. 
The whole amount of expulsive force of the voluntary muscles is, 
he says, not usually employed to assist the uterus in completing 
the second stage of labour; but this does not contradict the con- 
clusion we have ascribed to him. The conclusion is indeed, for 
Professor Haughton, inevitable, for every accoucheur knows that 
the bearing down efforts, whatever may be their actual measured 
power, are very strong, perhaps as strong as possible, quite fre- 
quently in ordinary labours. Besides, Haughton himself expounds 
his meaning in the following words : — “ It is plainly necessary that 
the first stage in the expulsion of the foetus should not be intrusted 
to a voluntary muscle, and hence an involuntary muscle is gradu- 
ally provided, which takes the initiative and commences the pro- 
cess of parturition, the completion of which is then accomplished 
by the aid of voluntary muscles, to the employment of which, at 
this stage, no moral objection can be raised. It is also necessary 
(if the Contriver be allwise, or if the principle of least action in 
nature be true), that the involuntary muscle so produced, should 
not possess more or less force than is requisite for its purpose. 
The uterine muscle does not grow to meet a growing resistance 
(as happens frequently in other cases), and 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 mem- 
branes it is called upon to rupture until the actual period of 
parturition has arrived.” 
The view expounded in these words has great authority on its 
side beside that of the quoted writer, for the point therein raised 
as to the relative powers and uses of the uterine and auxiliary 
