164 Viewpoints in tJie Study of Growth [Jan. 



eise of that capacity, which we must deal with. Here comes in a 

 factor which we learn from the study of regeneration." 



Experiments which have been conducted for some time by my 

 colleague Dr. Thomas B. Osborne and myself, imder the auspices 

 of the Carnegie Institution of Washington, make us hesitate to 

 accept some of the older dicta respecting the hmitation of growth 

 to a very definite period of Hfe. We have secured clear evidence 

 that the growth of rats and mice may be suppressed or held in abey- 

 ance for very long periods, even beyond the age at which any 

 marked increment of size ordinarily occurs, without loss of the 

 capacity of subsequent growth under appropriate conditions of diet. 

 It is necessary to distinguish clearly between growth and regenera- 

 tion or repair; for the latter is admittedly observed in the adult 

 period of life. 



The natural cessation of growth is a fact familiär to everyone. 

 As growth proceeds and the powers of the individual mature, his 

 tendency to grow rapidly declines. This is an interesting phenome- 

 non that has not been explained. Minot in particular has promul- 

 gated the view that there is from a very early period a marked fail- 

 ing in the capacity to grow, due to factors in the animal body itself . 

 The notion that senescence finds its beginning in the very earliest 

 periods of life is not a new one. Thus, Thomas Cogan, author of 

 The Haven of Health, writing in 1596, says : "And if we do con- 

 sider well the State of mankind in this life, we may see that a man 

 beginneth to die as soone as he is borne into this world, for that the 

 radicall moisture which is the roote of life, can never be restored 

 and made up againe, so good as it was at our nativitie, but continr 

 ually by litle and litle decaieth untill the last end of our life. Yet 

 by that moysture which commeth of nourishment, through meate 

 and drinke, it is preserved and prolonged, so that it is not so soone 

 wasted and consumed as otherwise it would be. Like as a lampe 

 by powring oyle moderately, the light is long kept burning, yet it 

 goeth out at the last. And this is it which Hippocrates speaketh: 

 The same heat which brought us forth consumeth us. Yet in the 

 beginning of our age while nature is yet strong, more of the nour- 

 ishment is converted into the substance of the bodie, than is con- 

 sumed : and that while the bodie increaseth and groweth. After- 

 ward so much only is restored as is wasted, and then the bodie is in 



