372 Proceedings of the Royal Society 
exert? I have a hand well accustomed to such work, and I find, 
by actual trial with an accurate dynamometer, 50 lbs. to be about 
the highest power I can use, situated as I am at the bedside in at- 
tendance on a case. I have ample reason, then, in such experience 
to believe that very few of the most powerful labours exert a force of 
50 lbs. ; that an ordinary strong labour is easily arrested by a 
much smaller force than 50 lbs. ; that the great majority of labours 
is accomplished by repeated efforts whose highest power never 
exceeds 25 lbs. I may add that, in the great mass of short forceps 
deliveries, the force required from the accoucheur, even when he 
delivers the head, unaided by the natural efforts, seldom reaches 
50 lbs. These statements are, to a great extent, arbitrary or 
dependent on my skill as an observer, yet I feel very confident of 
their accuracy. 
Again, the intelligent practitioner who has observed a case of 
difficult labour finished either by the long forceps or by podalic 
extraction, could not but form some rough idea of the force he 
used, and compare it with the force which the labour exerted in 
its nugatory struggles. The force which the accoucheur thus 
exerted would not be certainly the equivalent of what the labour 
must have put forth in order to produce a spontaneous termination. 
It would, no doubt, in most cases surpass the force which the 
mother must have exerted to produce the spontaneous birth. But 
it would be, nevertheless, a valuable measurement indicating a 
force which in such a case the labour failed to produce. Joulin 
and I have made dynamometrical experiments to make use of 
such measurements in estimating the highest power of labour. 
Another method of advancing our knowledge of this subject has 
been followed by the Rev. Professor Haughton. This gentleman 
does not, as his predecessors, examine the effects produced by the 
powers of labour, and thus get results having a very distinct positive 
value. He follows a plan which may be justifiable, yet which is 
difficult and dangerous. He takes an almost opposite method to 
that used by me. He measures the bulk and the extent of the 
involuntary and voluntary muscles employed in the function, and 
from these data he arrives at conclusions which he in one particular 
corroborates by a simple experiment. The results arrived at are 
statements of the powers of the parts, which are true if his methods 
