172 



SCIENCE. 



[Vol. X. No. 244 



MENTAL SCIENCE. 

 Brain-Growth and Body-Growth. 



The late Dr. Parrot of France was, at the time of his death, 

 collecting anatomical material for a study of the progressive de- 

 \'elopment of the several parts of the body as measured by such 

 characteristics as size and weight. Some of this material has been 

 arranged by Mile. Jeanne Bertillon, and presented by her to the 

 Anthropological Society of France. The problem there discussed 

 is the ratio of increase in weight of the brain to the increase in 

 weight of the body as a whole, of the height, of the heart, and of 

 the spleen. This is ascertained for the two sexes and for the vari- 

 ous ages, especially for the first years of life, when growth is at its 

 maximum. As will be seen, the results given are founded on a 

 sufficiently large number of measurements to make them generally 

 reliable. 



Expressing the weight of the body, of the heart, of the brain, of 

 the spleen, and the height, as i,ooo at birth, their condition at sev- 

 eral periods up to the sixth year is given in the following table : — 



Thus it appears that at the end of this period the height has 

 about doubled, the brain a little more than tripled in weight, and 

 the weight of the body, as of the heart and spleen, more than 

 quintupled. In another table is considered how much of this 

 growth of the first five years has been contributed by each of the 

 several periods of age above specified. From such a comparison, 

 it appears that the brain develops sooner and more rapidly in early 

 life than even the height. The percentage of the growth of the 

 first five years, that takes place in the first six months, is, for the 

 body-weight, only 13.66 for females, and 10.82 for males ; for the 

 heart, 11.43 snd 11.88; for the spleen, 19.7 and 19.0; for the 

 height, 20.8 and 11.40; while for the brain it is as much as 27.41 

 and 23.51 ; the first figure referring to the females, and the second 

 to the males. The same fact is more clearly brought out by saying 

 that at the beginning of the second year the female brain has al- 

 ready increased by 72 per cent of all the increase it will have made 

 within the first five years, while the body-weight has not reached 

 50 per cent of the development it will have at the sixth year. Ex- 

 pressing the total progress at the opening of the second year in 

 terms of the total progress at the opening of the sixth year, the 

 following table shows in detail the relative amount of growth at- 

 tained by the several parts : — 



The striking fact here is the advance of the female above the 

 male. This, it has been suggested, is what one ought to expect, on 

 the theory that the female organization is nearer the primitive type 

 than the male, for savages (and animals) are marked by a more 

 rapid march to maturity than civilized man. In actual weight and 

 height, however, the male, as is well known, exceeds the female ; 



and on the average during the first five years, taking the female 

 weight (and height) at 1,000, the male weight (and height) is shown 

 below. It may be noted that the brain-ratio between the two 

 sexes is larger than that of any other part. 



Greater changes take place within the first three months than 

 within the period from the third to the sixth month, but the maxi- 

 mum of growth takes place in the latter half of the first year. 



The sexual differences in these respects are very marked through- 

 out. The disparity diminishes within the first four years, to re- 

 appear in from the fourth to the sixth year with the same intensity 

 as in the first months of life. 



With which of the four measurements does the growth of the 

 brain in weight keep the most constant ratio ? Omitting the weight 

 of the spleen as unimportant and variable by pathological and 

 other causes, a glance at the following table will show that the 

 body-weight and the height give no such constant ratio. 



If, however, we compare the weight of the brain with that of the 

 heart, a more constant ratio is found, which Dr. Parrot would dig- 

 nify with the name of the ' encephalo-cardiac ' index to take rank 

 with other anthropological indices. The constant decrease of this 

 ratio with age is thus shown, taking 10 grams of heart to i gram of 

 brain. 



Ratio . . 

 No. of c 



It is probable that after the sixth year thfe ratio would tend to 

 remain constant. Be this as it may. Dr. Parrot has pointed out 

 an interesting line of research, and one calculated to shed much 

 light on the normal development of children. 



The Savagery of* Boyhood. — Mr. John Johnston, in an 

 article in the October issue of the Popular Science Monthly, brings 

 home the forcibleness of the analogy between the traits of savages 

 and that of developing civilized mankind. He cites a case of 

 wanton cruelty recorded, by a boy without any apparent feel- 

 ing for the cruelty of the act. Mr. Johnston, opposing the 

 sentiment that pervades much of the literature that is supposed 

 to be written for boys, does not predict for this boy a life of 

 sin, but gravely contemplates the trait as a step in the normal 

 development of youth. Pity is a late factor in moral evolution, and 



