Apeil 4, 1919] 



SCIENCE 



317 



temperament, which though elusive, has a real 

 existence and an imiwrtance hard to over- 

 estimate. Temperament is tlie expression of 

 these relations and one of the nice problems 

 the clinician has to face. 



Under certain circimistances it makes a 

 difiFerence whether one has light hair or dark, 

 not because these characters are themselves 

 important, but because they are indicative of 

 subtle dissimilarities in the chemistry of differ- 

 ent individuals, dissimilarities which are of 

 far-reaching importance for tlic individual as 

 a whole. 



Recently it has become possible to do our 

 laboratory work with animals the ages of 

 which are known. Working tlius we find at 

 every turn differences, distinct and definite, 

 dependent on the age, differences which should 

 be studied, for without shadow of doubt they 

 will be found in man when search for them 

 is made. 



I make no question tliat much of what I 

 have just said to you has a familiar sound, 

 but the time is coming, I feel sure, when the 

 significance of age will be appreciated in 

 many fields where now it is but little noted, 

 as for example in the blood, and I have spoken 

 thus to specially direct your thought to these 

 matters. 



Thus far the individual who is growing 

 normally and who represents the usual case 

 has been considered. In passing, however, it 

 may be worth while to turn for a moment 

 to the individual subjected to starvation. The 

 terrible years through which the world has 

 just passed have brought starvation vividly 

 before us. We know that in starvation growth 

 is modified and may apparently be stopped. 



As in so many other instances our knowl- 

 edge of the changes thus induced is still 

 fragmentary and incomplete. In the first 

 place we must distinguish between the starva- 

 tion which follows when tlie quantity of an 

 adequate diet is made imduly small, and the 

 case in which the diet is unbalanced and 

 defective in itself, and therefore only slightly 

 modified by quantitative variation. It is the 

 former case to which I would draw attention 

 here. 



If we may trust the tests with animals, two 

 systems tend strongly to resist mere quantita- 

 tive imderfeeding — the skeleton and the nerv- 

 ous system. Growth in them is greatly re- 

 tarded to be sure by underfeeding, but they 

 may still grow, while the body as a whole is 

 held at a constant weight or is even losing. 



The practical question before us however is 

 not so much the immediate effects of starva- 

 tion, as the response which such an animal 

 will make when it is brought back to a full 

 and normal food supply. 



The nervous system is best known to me and 

 I think we may say with regard to this system 

 tliat a return to the normal diet is followed by 

 nearly, if not quite, complete recovery. This 

 is a cheering and hopeful result and yet, as 

 always, a word of caution is in place. Starva- 

 tion, as followed in the laboratory, can be 

 studied free from the complicating conditions 

 of the exhausting systemic diseases, so often 

 associated with starvation in human com- 

 munities, and what is true for the simple 

 conditions of the laboratory may not be true 

 for those which are more complex. 



Nevertheless in these days, when underfeed- 

 ing is much in evidence, it is of interest to 

 note that one form of it at least does not 

 cause permanent damage to the great master 

 system of the bodj'. 



The life histories of many students and 

 productive scholars support this conclusion, 

 for biographies show only too frequently, 

 periods of starvation in the lives of those who, 

 then and later, were distinguished for intel- 

 lectual activity. 



Thus far I have been speaking of growth 

 as it modifies the patient, when that long- 

 suffering person is looked at as a biological 

 problem. 



Now let me pass to the second topic and ask 

 you to consider the growth of medical knowl- 

 edge. 



The mass of knowledge in any subject may 

 be likened to a sphere which is rolled on from 

 generation to generation, always growing by 

 additions on the surface. 



All of us, as scholars or investigators, are 

 entrusted with its preservation and its in- 



