532 A.H. Estahrook 



internal conditions; it has a strong tendency to grow in a perfectly- 

 definite way, at a definite rate, the rate giving a curve of a definite 

 form. It grows for a time in this way in spite of the almost com- 

 plete absence of the salts that are necessary for its continued 

 existence, and in spite of the presence of actively injurious chemi- 

 cals, which in a short time kill the organism. Whatever growth 

 occurs tends to follow the normal growth curve. The substances 

 within the organism, plus water, seem all that is necessary for 

 this process, and it persists for a time in spite of positively injuri- 

 ous external conditions. 



No evidence was found that a race of a given typical size can 

 be transformed by any of the chemicals studied into a larger or 

 smaller race. Their effects on growth seem due to interference 

 with the vital processes, resulting in pathological conditions in 

 other respects as well as in growth. Continued action of the chemi- 

 cals that interfere with growth usually sooner or later cause 

 death. The causes of the observed temporary changes in size 

 in a given race under differing cultural conditions are probably 

 to be sought for in variations m the nutritive and other conditions 

 of the normal environment, particularly in conditions that affect 

 the rate of fission. 



3. On the precise nature of the deleterious action on growth 

 in the case of the different chemicals the investigations gave little 

 light. In the case of sodium chloride it appears possible, as we 

 have seen, that a part of the injurious action is due to osmotic 

 pressure, while a part is not. But in the case of nicotine and 

 strychnine the minute quantites employed show that the osmotic 

 pressure plays no part, }et these chemicals produce essentially 

 the same effects on the growth as do undue amounts of sodium 

 chloride. In the case of alcohol the growth occurs in solutions 

 having a much higher osmotic pressure than the deleterious solu- 

 tions of sodium chloride. Thus all the facts taken together seem 

 to indicate that disturbance in osmotic relations plays little 

 part in producing the effects on growth, even in the case of such 

 substances as sodium chloride. 



4. As to the processes in growth itself, it appears clear that 

 the increase in size in early stages, up to 60 to 90 minutes (at 



