70 



Our source of confusion is the fact that what people com- 

 monly call the digestibility of food includes several very different 

 things, some of which, as the ease with which a given food- 

 material is digested, the time required for the process, and 

 the effect of different substances and conditions upon digestion, 

 are so dependent upon individual peculiarities of different 

 people and so difficult of measurement as to make the laying 

 down of hard and fast rules impossible. Why it is, for instance, 

 that some are made seriously ill by so wholesome a material as 

 milk, and others find that certain kinds of meat or vegetables 

 or sweetmeats " do not agree with them," neither chemist nor 

 physiologist can exactly tell.* Late investigations, however, 

 suggest the possibility that the ferments in the digestive canal 

 may cause particular compounds to be changed into injurious 

 forms, so that it may sometimes be literally true that " one 

 man's meat is another man's poison." But digestion proper, 

 by which we understand the changes which the food undergoes 

 in the digestive canal in order to fit the digestible portion to be 

 taken into the blood and lymph and do its work as nutriment, 

 is essentially a chemical process. About this a great deal has 

 been learned within a comparatively few years, so that here we 

 have many important facts that have not yet got into current 

 literature. 



The average man swallows, say six pounds of food and 

 drink, meat, fish, potatoes, bread, coffee, milk, water, and what 

 not, per day. Every twenty-four hours, then, all the solid sub- 

 stance, all the protein, fats, carbohydrates and mineral matter 



* Things do not always or, indeed, often come to hand exactly when they fit best, but, oddly 

 enough, just as I am writing this the postman brings a letter from the Recording Secretary of the 

 American Fisheries Society with the following statement : "By the way, I cannot digest oysters, 

 raw or cooked, but can eat clams both Venus and Mya) and can go to bed on the outside of a 

 lobster mayonaise. Coffee ties a hard knot in the interior department, buckwheat cakes start my 

 ' vinegar factory ' to work on full time, beans cause the 'gas works' to be put in operation. This 

 merely proves the adage about 'one man's meat, etc' " The learned gentleman follows this by the 

 statement that he has already passed the age of forty, at which a man is said to become "either a 

 fool or a physician" ; and gives a physiological explanation of his dizestive temperament which he 

 attributes to dyspepsia "aggravated by nine months' diet on corn meal, ground cob and all, and 

 aorghum syf up, in Confederate prisons." Of course it would be wrong to affirm that in this especial 

 case it is the microbe tha* causes the protein of the oysters to be changed into compounds which 

 make them disagree, or produces the disagreeable fermentations in the buckwheat cakes and beans, 

 but some how or other different food-materials do produce very disagreeable effects in the digestive 

 apparatus of different people, and the science of to-day expliins this in part by the action of the 

 digestive ferments, among which microbes play an important role. 



