November 15, 1907] 



SCIENCE 



671 



of a new metliod or a new point of view, and 

 we must beware of assuming that a study of 

 food energy will solve all the problems of 

 nutrition. At the same time, the new method, 

 while not a panacea, has proved a most useful 

 instrument which seems likely to be employed 

 to an increasing extent. 



The unit of energy commonly employed in 

 such studies is either the large or small 

 calorie. This arises naturally from the fact 

 that in order to measiire the quantities of 

 energy involved we ordinarily convert them 

 into heat. The use of the calorie as a unit 

 is, therefore, convenient in avoiding a recal- 

 culation of results, in spite of its unfortunate 

 suggestion that we are dealing with energy in 

 the animal body in the form of heat only. 



In practical use in connection with the feed- 

 ing of domestic animals and the computation 

 of their rations, however, the calorie is an 

 inconveniently small unit. To express the 

 energy values of feeding stuffs per pound in 

 kilogram calories requires rarely less than 

 three integers and usually four, while the 

 energy values of rations computed per 1,000 

 pounds live weight, as is the usual custom, 

 practically never require less than five in- 

 tegers. Taking, for example, the mainte- 

 nance requirement, which is about the smallest 

 quantity of energy which we need to express 

 in practise, the average of Kellner's determi- 

 nations for cattle is 13,469 calories of metab- 

 olizable energy per head, or 21,312 calories 

 per 1,000 kgs. A ration for productive pur- 

 poses, of course, would require the use of still 

 larger numbers. These large numbers are in- 

 convenient in computation, and differ so much 

 in appearance from those which have previ- 

 ously been used that it is likely to be difficult 

 to bring them into common use. 



To meet this difficulty Kellner has proposed 

 the use of " starch values " to express the pro- 

 duction values of feeding stuffs as determined 

 according to his method. The starch value of 

 a feeding stuff means, in brief, the amount of 

 pure starch which would produce the same 

 energy effect as a unit weight of the feed in 

 question. Computed per 100 units, the starch 

 values give figures comparable with the per- 

 centages of total digestible matter heretofore 



used, commonly requiring two integers for 

 their expression. 



There are, however, certain objections to this 

 method of expression, and to the writer it 

 seems preferable, if we are to attempt to deal 

 with energy values at all, to do so boldly and 

 to employ a unit of energy rather than a unit 

 of matter. To do so conveniently, as already 

 indicated, it is desirable to have a larger unit, 

 and the object of this paper is to suggest such 

 a unit for discussion and to indicate by one 

 or two examples how it could be used. 



The unit which I suggest is 1,000 kilogram 

 calories, for which I propose the designation 

 Therm. The word therm has already been 

 proposed as the equivalent of the small or 

 gram caloric, but does not appear to have 

 come into general use. Following the analogy 

 of the calorie, we may write the unit here 

 proposed with a capital and use the capital or 

 full-face T as a convenient abbreviation. The 

 relation of the units would then be 



1 therm (t) = 1 gram-calorie (eal.). 

 1,000 cals. ^1 kilogram-calorie (Cal.). 



1,000 Cals. =1 Therm (T). 



While a sense of strangeness and awkwardness 

 of course attaches to the proposed as to any 

 new term, it seems better, if a new unit is 

 to be used at all, to give it a new name rather 

 than to employ any modification of the word 

 calorie, which would be likely to produce con- 

 fusion. It may be objected that the suggested 

 unit is not a C.G.S. unit, but while this is 

 true, a thermal unit is practically more con- 

 venient, partly because, as already pointed out, 

 our determinations of energy are usually made 

 in thermal units and in part because any 

 available C.G.S. units are rather small. 



As an example of the use of the suggested 

 new unit, I have taken three samples of feed- 

 ing stuffs whose energy values have been de- 

 termined at the Pennsylvania Experiment Sta- 

 tion, namely, timothy hay, clover hay and 

 corn meal. The composition and digestibility 

 of these feeding stuffs per 100 pounds as ex- 

 pressed by the ordinary method, and also the 

 energy values of the same quantity, are shown 

 in the following table : 



