24 FOODS AND FOOD ADULTERANTS. 



error in such experiments, and it is very probable that the proportions actually di- 

 gested were somewhat larger than these figures imply. Very likely each of the two 

 persons may have digested practically all of the fat of the butter, and all but 1 or 2 

 per cent, or even less of that of the oleomargarine. In these experiments the butter 

 and oleomargarine were eaten with bread, cheese, white of eggs, potatoes, peas, and 

 sugar. 



The digestibility of butter has been tested in two or three other series of experi- 

 ments. Thus Dr. Rubuor, in Munich, found that a healthy man, on a diet of but- 

 ter, bread, and meat, digested 97.3 per cent, of the total fat of the food, of which the 

 bulk came from the butter. In some experiments by myself, in which a man received 

 a diet of fish (haddock) and butter, 91 per cent, of the total fat, nearly all of which 

 came from the br.tter, was found to be digested. 



The experiments of Rubuer and myself were conducted in the same manner as 

 those of Mayer, and exposed to the same slight sources of error. The results of all 

 of them are just what would naturally be expected, namely, that very nearly all of 

 the fat of butter and of oleomargarine is digested in a healthy organism. 



It might seem that the relative digestibility of the two materials could be tested 

 by experiments in artificial digestion ; that is to say, by treating both substances 

 with digestive fluids, or with materials similar to them, and observing the results. 

 Such experiments are not accurate tests of the actual digestibility of the substances 

 in the body, since the conditions which obtain in the alimentary canal cannot be ex- 

 actly imitated by any artificial means which physiological chemistry has yet sug- 

 gested. Professor Mayer, taking into account that the fats are more or less split up 

 in the process of natural digestion, has made some experiments to test the compara- 

 tive readiness with which butter and oleomargarine are split up, and finds a very 

 slight difference in favor of butter. As the result of all his experiments he concludes 

 that, while the butter appears to be a little more digestible than oleomargarine, the 

 difference is too small to be of practical consequence for healthy persons. At the 

 same time there may be cases, especially those of invalids and children just past the 

 nursing period, when butter would be preferable; but, considering simply the nutri- 

 tive values for ordinary use, Professor Mayer considers the choice between the two 

 to bo essentially one of comparative cost, an opinion from which there is, so far as I 

 am aware, scarcely any dissent among those who have devoted the most study to this 

 class of subjects. 



It is a common and perhaps correct theory, though it lacks experimental confirma- 

 tion, that the flavor of the fats peculiar to butter may in some way increase its value 

 for nutriment. But, granting this to bo true, it would bo hardly reasonable to as- 

 sume that a difference in flavor which even experts may fail to detect could make any 

 considerable difference in the nutritive effect of two substances otherwise so similar 

 as real and imitation butter. 



To recapitulate briefly, butter and oleomargarine have very nearly the same chemi- 

 cal composition ; in digestibility there may bo a slight balance in favor of butter, 

 though for the nourishment of healthy persons this difference can hardly be of any 

 considerable consequence ; for supplying the body with heat and muscular energy, 

 which is their chief use in nutrition, they are of practically equal value, excelling 

 in this respect all other common food materials. Such, at any rate, is the practically 

 unanimous testimony of the latest and best experimental research. 



While it is true that chemical analysis and certain digestive experi- 

 ments have not hitherto shown that pure butter possesses any marked 

 superiority over butter surrogates as a food, yet it must not be forgot- 

 ten that butter has a much more complex composition than lard or tal- 

 low or cotton-seed oil; that it is a natural food, and doubtless possesses 

 many digestive advantages which science has not yet been able to 

 demonstrate. 



