284 PHYSIOLOGY CHAP. 



(the front incisors do not begin to fall out and the second ones to 

 appear till the child is seven years old). 



During this second period mastication takes the place of 

 suction, and the child's diet is more like that of an adult ; he walks 

 more and more steadily, and his movements are quick, easy, and 

 exuberant ; his psychic life is lively and tumultuous, and his 

 fluency of speech correspondingly greater. During this second 

 period, earlier in girls than in boys, the secondary sexual charac- 

 teristics begin to appear, so that from the figure as a whole and 

 the bodily development, the sex may be guessed without evidence 

 concerning the sexual organs. 



Ftirst describes a state of relative anaemia as occurring at the 

 close of this period (from 5 to 7 years of age) and coinciding with 

 excessive thinness and rapid increase in height ; to this he gives 

 the name anaemia of growth. 



(c) The third period of childhood (boyhood or girlhood) lasts 

 from the sixth or seventh year to the age of puberty. When the 

 second teeth have been cut, from seven years old onwards, it may 

 be said that all the other organs and tissues, with the exception 

 of the generative cells which are still undifferentiated, have 

 attained almost the same relative stage of development and that 

 their further growth will proceed on parallel lines. This period 

 presents no characteristics necessitating its subdivision into 

 stages ; its length varies with climate and various racial and social 

 conditions. In our climate it ends with puberty in girls at from 

 13 to 15 years of age, iff boys at from 15 to 18 (see Chapter V.). 

 Basing his conclusion on 31,659 cases, Rossi-Dona (1908) has 

 established the average age for Italian girls at the time of the 

 first menstruation as 14 years, 5 months, and 22 days. From the 

 anatomical point of view, however, the body in our race only 

 attains its full development later, as is also the case with the 

 sexual functions. Lange considers that the female body ceases to 

 grow at 19 years of age, the male at 20 ; there are, however, 

 numerous cases of women whose maximum growth has been 

 reached at 24 to 28 years of age and of men at 30 to 34 years, 

 though growth after the twentieth year is slow and limited. In 

 Chapters IV. and V. we have already treated of the general and 

 particular changes which mark the beginning of puberty in the 

 two sexes. 



Various authors have endeavoured to establish by measure- 

 ments the average growth. These investigations, which were 

 begun by Quetelet, the director of the statistical office in Brussels, 

 on the infant population, were repeated by Bowditch on the 

 children of Boston, and carried further by Pagliani, Geissler, 

 Ultzsch, and Daffner. The averages obtained by the different 

 authors vary considerably. Stratz distinguishes normal values 

 for growth (which are probably higher than average values) 



