374 
Proceedings of the Royal Society 
as to the comparative value of the two forces which combine to 
produce the power which is to be measured. 
The results given in Professor Haughton’s paper which appear 
to me to be both new and important are three. I shall first state 
them, and then proceed to their examination one by one 
1. The first conclusion is, that “ the uterine muscles are capable 
of rupturing the membranes in every case, and possess in general 
nearly three times the amount of force requisite for this purpose.” 
.... “It would be a waste of power (adds Haughton) to endow 
the uterus with more force than I have shown it to possess, for it 
is not necessary that the uterus should complete the second stage 
of labour, as the abdominal muscles are available for this purpose ; 
so that by using them, and not giving the uterus more force than 
is absolutely necessary for the first stage of labour, an admirable 
economy of muscular power is effected.” ... “ The extreme 
force of uterine contraction produces a pressure of 3402 lbs. per 
square inch, which is equivalent to a pressure of 54406 lbs. acting 
upon a circle of four and a-half inches in diameter, which is 
assumed as the average area of the pelvic canal.” 
2. The second of Professor Haughton’s new and important 
conclusions is, that the action of the voluntary abdominal muscles 
“ constitutes the chief part of the force employed in difficult 
labours.” . . . “ The amount of available additional force given 
out by the abdominal muscles admits of calculation, and will be 
found much greater than the force produced by the involuntary 
contractions of the womb itself.” 
3. The third conclusion is, “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.” ... “ Adding together the combined forces of the 
voluntary and involuntary muscles, we find — 
Involuntary muscles . . = 5440 lbs. 
Voluntary muscles . . = 523-65 lbs. 
Total . . 577-75 lbs. av.” 
I. The first of Professor Haughton’s conclusions on which I 
comment is, to the effect that the unaided uterine muscle can 
