NUTRITION. 355 



proteins from other sources. Only by boiling with 60 per cent alcohol 

 containing 0.2 per cent of sodium hydroxide have we been able to 

 extract any considerable part of it. We expect to publish the results 

 thus far obtained in the near future, and shall continue work on this 

 subject in the hope that before long we shall learn something of the 

 chemistry, as well as of the nutritive properties, of this peculiar type 

 of protein which ^vill be of value. 



Attention has also been given to the hj^drolytic action of dilute 

 alkalies at 100° on proteins. This work, which is an extension of our 

 earlier study of the different forms of nitrogen in protein bodies, promises 

 results of interest and will be continued as opportunity presents. 



Many of the so-called practical feeding experiments made in the past 

 were done apparently with little appreciation of the complexity of the 

 factors involved ; hence the results obtained proved disappointing when 

 attempts were made to apply them in practice. For example, the 

 farmer has been instructed to feed a given proportion of protein (the 

 so-called nutritive ratio) if he is to expect maximum yields in 

 feeding for growth, milk production, eggs, fattening, or simply main- 

 tenance. In determining the proper proportion of protein for these 

 different types of feeding, no attention had been paid to the quality of 

 the protein, the proportion ha\TLng been estabhshed simply by feeding 

 a few animals on rations customarily in use at the time the experiments 

 were made. Experience on the farm soon showed that this method 

 had serious limitations, and inasmuch as so many kinds of protein con- 

 centrates have come into general use, few farmers are to be found who 

 do not also give consideration to the kind of protein these furnish. In 

 other words, the farmer has learned by practical feeding that the 

 kind of protein does make a difference in the amount of product he 

 obtains and that the nutritive ratio alone is not a sufficient guide. 

 His experience is in full accord with what we have learned about the 

 relative nutritive value of the different proteins in our investigations 

 conducted under pre\'ious grants, and emphasizes anew the importance 

 of extending this knowledge so that agricultural practice of feeding can 

 be put on a truly scientific basis. Now that methods of feeding have 

 been developed which permit changing one factor at a time, this same 

 method is being used by others to study the nutritive requirements of 

 domestic animals in such a way that results of real value are being 

 obtained. 



Our feeding methods, permitting as they do the study of individual 

 constituents of the ration, have also been found useful in studying the 

 effect of poisons and various drugs, and, indeed, have opened up a large 

 field for investigations of various kinds. These methods are already 

 being employed by the Bureau of Chemistry of the Department of 

 Agriculture. 



