222 THE HUMAN SPECIES 



smell. The specific gravity ranges from 1006 in sheep and 

 goats up to 1060 in horses. Large quantities of urea and 

 hippuric acid (horse), aromatic sulphates and carbonates of the 

 alkalies and alkaline earths are present, but only small amounts 

 of phosphates. A further difference between the omnivora and 

 the carnivora and herbivora is seen in the relative output of 

 water by the urine and respiration upon ordinary diet. 



OUTPUT OF WATER. 



Carnivora in urine 70 7 in respiration 30 / o 

 Herbivora 30 ,, 70 



Omnivora ,, 60 40 ,, 



2. Reproductive Organs. 



A point in which man and all the metazoa manifest com- 

 plete agreement lies in the fact that in order to maintain the 

 species the body is equipped with special glands sexually dif- 

 ferentiated which become functionally active when a certain 

 period of growth has been reached. 



Puberty, the period in life when the sexual glands begin to 

 secrete their procreative products, occurs in man relatively late, 

 in boys at fourteen to sixteen, in girls thirteen to fifteen, in 

 tropical races a year younger. The late onset of puberty is 

 particularly marked when contrasted with domestic animals ; 

 for instance : 



Horse at 18 months 



Cow and bull ,, 8-12 ,, 



Sheep ,, 6-8 ,, 



Pig 5-8 



Dog 6-8 



Camel 5 years 



Llama ,, 4 ,, 



Whether the statement is correct that the large old-world 

 apes are sexually mature at four years must remain undecided. 1 

 In wild animals observations and statements are still more 

 scanty and unreliable upon this point. 



The onset of puberty is further accompanied by secondary 



"'Darwin, loc. cit., v., n, states that the anthropoids (orang) do not reach 

 puberty before the tenth to fifteenth year of life. 



