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SCIENCE. 



[M.S. Vol. XV. No. 381. 



crops must be practiced, and as far as 

 possible diseased material, and the car- 

 riers of such material, must be destroyed. 

 I lay much stress upon the last statement. 

 Insects in particular are responsible for 

 much more than the direct damage they 

 cause. 



The men who enter this field from now 

 on must have a better training and a more 

 versatile one than those who have culti- 

 vated it in time past, and the emphasis 

 should be placed on laboratory work and 

 laboratory training. It goes without say- 

 ing that the man who would become a use- 

 ful pathologist must have considerable 

 familiarity with the literature of his sub- 

 ject. In other words, he must know how 

 to use literature, and must be a linguist, or 

 able to command linguists. He ought also 

 to have a very considerable amount of 

 technical training in physics and chemis- 

 try and should know something of zoology. 

 In the way of preliminary training, eight 

 years of university M'ork, or its equiv- 

 alent, is not too much, and a very consid- 

 erable part of at least four years of this 

 time the student should spend on organic 

 chemistry. He must not expect to accom- 

 plish very much as a pathologist unless he 

 has also become familiar with a very con- 

 siderable body of knowledge respecting the 

 behavior of plants under normal conditions. 

 In other words, to be a good pathologist 

 he must be a good physiologist, and to be 

 , 3 good physiologist he must first be a good 

 chemist and physicist, for at bottom 

 physiology rests on chemistry and physics, 

 and the advances in this line during the 

 next fifty years will undoubtedly be made 

 by men who approach the problems of 

 biology from the standpoint of physiolog- 

 ical chemistry. Given all this, and still the 

 man will not be eminently successful unless 

 he is a born experimenter; I mean by this 

 one capable of reasoning closely, and of de- 

 vising ingenious methods of extorting from 



nature her well hidden secrets. This is, 

 of course, asking a good deal of one man, 

 and is more, perhaps, than can be expected 

 of most men. Very likely a solution of 

 the question will be found in many cases 

 by a union of forces. No man is likely to 

 solve these problems who approaches them 

 from the purely chemical standpoint. 

 Something more is required. The pathol- 

 ogist should be the guiding mind, but he 

 must associate with himself a competent 

 physiologist and one or more skilled chem- 

 ists having some flexibility of mind and a 

 decided inclination to study living things 

 rather than dead things. The old routine 

 ash analyses of the chemist are of no help 

 to us. We wish to know the proximate 

 rather than the ultimate elements of the 

 plants we are studying, and to know how 

 these vary in quantity and kind under 

 changed conditions. In other words, what 

 we wish to know is not how much carbon, 

 hydrogen, oxygen, nitrogen, potash, phos- 

 phoric acid, etc., the plant contains, as de- 

 termined by ash analyses, but in what form 

 it exists in the living plant. We wish to 

 know the kind and quantity of each of the 

 organic acids, and how they vary in 

 amount from time to time under changing 

 conditions. We wish to know all about 

 the sugars, the fats, the tannins, the pro- 

 teids, the amids, the giucosides, the en- 

 zymes, etc., changes in all of which play an 

 important part in nutrition and in predis- 

 position to disease. How are these sub- 

 stances increased, diminished or changed 

 by changing external conditions, either 

 natural or of man's devising, e. g., by foods 

 added to the soil, by fungicides sprayed 

 upon the foliage, by heat, or cold, sunshine 

 01' cloudy weather, drought or excessive 

 precipitation? We desire to study the 

 chemical-physiological requirements of the 

 parasites in the same minute way. Then 

 we shall be able to put the two kinds of 

 evidence together and begin reasoning. 



