1] 



UPON THE RATE OF GROWTH 



331 



TABLE XXXIV 



SHOWING FOR VARIOUS MAMMALS THE TIME REQUIRED TO DOUBLE THE BIRTH- 

 WEIGHT, THE PERCENTAGE OF 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 G-rowth by 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- 



