1914] Lafayette B. Mendel 167 



tion are a common cause of slow growth; but even with adequate 

 diet there may arise a condition of maintenance without growth. 

 Here we enter the realm of dwarfed or stunted individuals. The 

 complete suppression of growth has been accompHshed by Osborne 

 and myself in a variety of ways which are not primarily attributable 

 to underfeeding. The energy factor, as such, thus drops out of the 

 problem. In this respect the experiments are not comparable with 

 those of Waters and of Aron, both of whom accompHshed their 

 results by underfeeding with adequate food materials. In our ex- 

 periments the " energy requirement for maintenance " and the 

 "energy requirement for growth," which together are essential 

 to the developing organism, were both supphed. Our dwarfed 

 rats did not grow primarily at the expense of stored tissue mate- 

 rials : in respect to gross form they apparently f ailed to grow in 

 any sense. If it is true that growth can only continue when the 

 energy intake exceeds the mere maintenance requirement, it is 

 equally true that an excess of calories does not per se insure growth 

 in a suitable animal. This fact furnishes an opportunity to the in- 

 vestigator to ascertain and difTerentiate some of the essential quali- 

 tative factors : protein, inorganic salts, etc. — their minimum and 

 Optimum values. 



Progressive decline in weight, negative growth (kataplasia), is 

 an obviously pathological manifestation. Like most of the abnor- 

 malities of the adolescent period its clinical manifestations are of 

 decided importance. 



Irregularities of growth in the individual tend to be followed by 

 compensating processes. Statistical studies on children, for in- 

 stance, indicate that retardation in early growth is made up by 

 abnormally rapid growth later. Whether all growth really stops 

 in such instances, or whether our measurements do not merely indi- 

 cate a loss of special body substances such as stored nutrients, needs 

 to be determined. The answer has a bearing on the question 

 already raised whether in the recovery process we are really dealing 

 with new growth or with restitution of depleted tissues. 



Attempts to influence growth by drugs, such as alcohol, nicotine, 

 caffeine, etc., are recorded in the literature. They need not be de- 

 tailed in this connection. It should be remembered that the obvious 

 efifects are not the only ones which may enter into the pathology of 



