366 Experimental Zoology 



Thus, despite the different conditions, social and politi- 

 cal, in different countries, the proportion remains nearly the 

 same. 



These figures give the birth rate. The proportion differs con- 

 siderably from the proportion of adult males to females; for 

 in Europe, for example, there are 1000 men to every 1024 

 women. Thus the adult proportion is the reverse of the pro- 

 portion at birth ; or, in other words, the excess of males at birth 

 is more than made up by the greater death rate of boys as 

 compared with that of girls. 



Local conditions also affect the proportion, for in Italy and 

 in the Balkan Peninsula there are more men than women. 

 As stated, the death rate of male children in Europe is known to 

 be greater than that of female children. At about' the twelfth 

 to the fifteenth year the numbers become equal. After the 

 thirty- fifth year the men die oftener than the women, which finally 

 brings about the conditions mentioned above. Male children 

 appear less resistant than female, and adult males die more 

 often from greater exposure to danger, from alcoholism, and 

 from crime, etc. 



For animals the following records have been collected by 

 Lenhossek : 



MALES FEMALES 



Horse 98 .31 100 (Dusing) 



Cattle . i7-3 i (Wilchens) 



Sheep 97.7 100 (Irwin) 



Pig . . . . . . . iii.S 100 (Wilchens) 



Rat 105.0 100 (Cuenot) 



Dove ........ 105.0 100 (Cueriot) 



Hen 94.7 100 (Darwin) 



Grassfrog 82.0 100 (Cuenot) 



Fly 96.0 100 (Cuenot) 



There are some other remarkable cases in the vertebrates. 

 Pfliiger found the disproportion between male and female 

 frogs reared from eggs to be astonishingly great. This led him 

 to examine the proportion of adult males and females in the 



