§1] 



UPON THE RATE OF GROWTH 



331 



TABLE XXXIV 



Showing fok Various Mammals the Time eequieed to double the Bikth- 

 WEiGHT, the Percentage oe Different Organic Constituents in the 

 Milk, and the Relative Quantity of Albumen, Calcium Oxide, and 

 Phosphoric Acid in the Milk of the Different Species — the Quan- 

 tity IN Man being taken as the Standard 



From this table it is clear that there is a close relation 

 between rate of growth and the percentage of albumen only 

 among the organic substances of milk. This relation is best 

 brought out by comparing columns 2 and 5. The last two col- 

 umns show a close relation between growth and the quantity 

 of calcium and phosphorus in the milk. But of the organic 

 substances the quantity of the nitrogenous compound deter- 

 mines the rate of growth. 



3. Growth as a Response to Stimuli. — Hitherto we have 

 regarded the process of growth in too mechanical a way, as 

 though certain nutritive compounds, passing into a chemical 

 mill, were inevitably transformed, at a certain rate, into proto- 

 plasm or formed substance. We have now to recognize that 

 the growth processes are essentially vital processes, and, as 

 such, characterized by all that complexity which we find in 

 such a vital process as response to stimuli. 



a. Acceleration of Growth hy Chemical Stimulants. — Many 

 chemical agents which are not themselves food may stimulate 

 the growth processes. We have already seen (p. 51) how 

 certain poisons cause, in dilute solutions, accelerated move- 



