VOL. LXXVI.] PHILOSOPHICAL TRANSACTIONS. 125 



mortality is -^ less, 4- more of the male sex die, and near double the number is 

 still-born. To what then are we to attribute this lessened mortality in favour of 

 male twins .^ Probably to their brain and nervous system suffering less during 

 delivery, on account of their heads being much smaller than those of single 

 children. There is one circumstance remaining, relative to the proportion of 

 the sexes, which may be noticed. We see evident wisdom in the creation of a 

 greater number of males than females; but why the proportion they bear to each 

 other differs in different countries and situations, and why there should be a 17 th 

 more males born of single children than twins, are questions which he leaves to 

 be decided by those philosophers who understand the theory of generation better 

 than he does. Be this as it may, he is convinced that the majority in favour of 

 the male sex is sooner destroyed than the generality of writers seem to be aware 

 of. Did the limits of this letter permit, he thinks he could prove from Dr. 

 Short's own data,* that the majority of males is destroyed long before the com- 

 mon marriageable period; but he contents himself with an observation or two on 

 the registry before us. If -i- of the whole born in this hospital die before 3 years, 

 which is the established computation for great cities ; and if, on the loss of some- 

 what more than a third of this half, a majority of 1 177 be reduced to 483 by a 

 loss of 694, as appears from the registry, it is pretty evident, that by the death 

 of the 2 remaining thirds, a majority will be left in favour of the female sex. It 

 is obvious, that the statement with regard to twins corroborates this supposition : 

 for of them instead of 4-, there is near 4- dead and still-born, the consequence of 

 which is, that we send out a majority of females. It may be objected, that their 

 males do not bear so great a proportion to the females; and that therefore it is 

 not to be expected they should keep up their majority so long. But there is onlv 

 a 17th fewer males produced; whereas it has been already shown, that there is a 

 much greater proportion between the deaths of single and twin males against the 

 former, and in favour of the latter. 



In his 2d letter Dr. Clarke states, that with the view of ascertaining how far 

 some of the foregoing conjectures are well founded, and of determining with 

 D-reater precision the more obvious differences between the male and female sex 

 in infancy, he began in July 1785, by weighing 40 children, 20 of each sex, 

 and by taking the dimensions of their heads. In the months of August and 

 Sept. he repeated the same experiment twice, taking such children as appeared 

 to have arrived at the full period of gestation promiscuously as they happened to 

 be born. He weighed them all a few hours after birth, before they had taken 

 food, and beforp purgative medicines had time to operate. For this purpose, he 

 made use of a small spring or pocket steelyard, which weighs any thing not hea* 



New Observations, p. 72, et seq. — Ori; 



0' 



