370 Proceedings of the Royal Society 
of three was either not recognised or has not been stated. Five, 
however, are known to have been males — a circumstance of con- 
siderable interest, as it serves to corroborate the statement made 
by Mr Thomas Beale, in his work on the natural history of the 
sperm whale, that “ the large and fully-grown males always go 
singly in search of food.” 
5. On the Efficient Powers of Parturition. By Dr J. 
Matthews Duncan. 
There can be no doubt that, among the numerous matters at 
present occupying the attention of obstetricians, none is more 
important than the subject of this paper. So evident is the cor- 
rectness of this statement that one cannot but wonder why 
attempts to arrive at the truth have been, so far as we know, 
delayed till the present day. It is long since excellent researches 
of an analogous kind in regard to the force of the circulation of 
the blood, the power of the ventricles of the heart, were pub- 
lished ; yet such researches do not seem naturally so attractive, nor 
do they give promise of so valuable practical results as those into 
the power of labour. 
It is well known that the first and, I believe, the best results in 
this inquiry have been obtained by careful deduction from experi- 
ments on the tensile strength of the amniotic membrane. The 
researches referred to were made quite independently, and pub- 
lished soon after one another by Poppel, of Munich, and by Tait 
and myself conjointly. Studying this subject, I thought of some 
other modes of reaching conclusions, such as by observations on the 
caput succedaneum. Means might be taken to find the force 
required to raise a caput succedaneum, and the variations of force 
required to raise this swelling in different degrees of thickness. 
Such an investigation would, no doubt, lead to similar valuable 
results, but the plan has never been employed. Again, observa- 
tions might be made to ascertain the force required to rupture the 
fourchette or the perineum, and thus a fact might be got which 
would be of service in this inquiry. It is well known to 
accoucheurs how these parts sometimes offer a successful resistance 
to all the powers of labour. This resistance, if its force be ascer- 
