88 



THE RATE OF GROWTH 



[CH. 



twenty seconds or so, and after each little increment there is a 

 partial recoil. 



Fig. 17. Pulsations of growth in Crocus, in micro-millimetres. 

 (After Bose.) 



The rate of growth of various farts or organs*. 



The differences in regard to rate of growth between various 

 parts or organs of the body, internal and external, can be amply 

 illustrated in the case of man, and also, but chiefly in regard to 

 external form, in some few other creaturesf. It is obvious that 

 there hes herein an endless field for the mathematical study of 

 correlation and of variabihty, but with this aspect of the case we 

 cannot deal. 



In the accompanying table, I shew, from some of Vierordt's 

 data, the relative weights, at various ages, compared with the 

 weight at birth, of the entire body, of the brain, heart and hver ; 



* This phenomenon, of incrementum inequale, as opposed to incrementum in 

 iiniversum, was most carefully studied by HaUer: "Incrementum inequale multis 

 modis fit, ut aliae partes corporis aliis celerius increscant. Diximus hepar minus 

 fieri, majorem pulmonem, minimum thymum. etc." (Elem. \ui (2), p. 34). 



f See [inter alia) Fischel, A., Variabilitat und Wachsthum des embryonalen 

 Korpers, Morphol. Jahrb. xxiv, pp. 369-404, 18fi6. Oppel, VergUichung des 

 Entwickelungsgrades der Organe zu verschiedenen Entwickelungszeiten bei Wirbel- 

 thieren, Jena, 1891. Faucon, A., Pesees ef Mensurations fcetales n differents ages 

 de la grossesse. (These.) Paris, 1897. Loisel, G., Croissance comparee en poids 

 et en longueur des foetus male et femelle dans I'espece humaine, C. R. Soc. de 

 Biologie, Paris, 1903. Jackson, C. M., Pre-natal growth of the human body and 

 the relative growth of the various organs and parts. Am. J. of Anat. ix, 1909; 

 Post-natal growth and variability of the body and of the various organs in the 

 albino rat, ibid, xv, 1913. 



