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 : — 
Mates FEMALES 
Horse . 2 . é Z - : i 98.31 100 (Dusing) 
Cattle . 3 : r : ‘ A 107.3 too (Wilchens) 
Sheep . ‘ 3 ‘ ‘ : F ‘ 97.7 too (Irwin) 
Pig : 4 : : ‘ : : ‘ 111.8 zoo (Wilchens) 
Rat. F : z : F : F 105.0 roo (Cuénot) 
Dove . 3 . ‘ é : 4 , 105.0 too (Cuénot) 
Hen . ; ‘ : . : : : 94.7 too (Darwin) 
Grassfrog . F 3 ‘ - F 2 82.0 too (Cuénot) 
Fly. : % : , : g : 96.0 too (Cuénot) 
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 
