TRANSACTIONS OP THE SECTIONS. 115 



made. There seem also to be groimda for the belief that our knowledge of the 

 active properties of tea and coffee is not yet complete. It is singular that in the 

 market the only test applied by the merchant is the flayour, which doubtless mainly 

 depends upon the essential oil of the leaf, whilst in the laboratory the test is the 

 quantity of theine ; the former, viz. the aroma, varies greatly in the different speci- 

 mens of tea, whilst the latter (the theine) may be as abundantly found in the low- 

 priced as in the high-priced teas. There is an agreeable effect produced by tea 

 which the theine does not account for, and thence it is inferred that there must be 

 some hidden quality in tea which produces it ; but when we refer to the poor man's 

 tea, to 2 ozs. of tea per week for a family, used thrice a day, affording not more 

 than half a teaspoonful of tea for the whole meal of a family, it is difficult to belie^'e 

 that much more influence is found in the cup than that of a pleasant warm di'ink, 

 and one the use of which is universal and fashionable. 



The physiology of foods is in a less satisfactory state than that of their chemical 

 constituents, and as it is a much more recondite question, the latter has perhaps too 

 exclusively usui-ped its place in detei-miuing the value of foods. 



Thus, the husk of grains, even the inner part which is directly in association with 

 the fecula, contains a larger proportion of niti-ogenous matter than is foimd in the 

 fecula, and thence it has been inferred — nay, in spite of every exposure of the fallacy, 

 it is still maintained by those interested in bread companies, that the meal deiived 

 from the whole grain is more nutritious than that obtained from the fecula alone. 

 In periods of famine the bark of trees has been selected for food, because it contains 

 a certain amoimt of starchy matter, and the wood of plants, when sa^vn into a line 

 powder, has been mixed with other substances and eaten as food ; but because the 

 sawdust is rich in nitrogen, as rich as is the husk of seeds, would it not be repug- 

 nant to common sense to affirm that it is not only a good food, but that wheaten 

 flom* would be a better food with a portion of sawdust added to it ? Yet such is 

 precisely the state of the question with regard to the bran or the husk of grain ; it is 

 indigestible in the human stomach, and when eaten as food, all the indigestible part 

 remains unused, and in passing through the bowel acts as an irritant and laxative. 

 Hence the digestibility of various foods is a prime element in the calculation of 

 the nutritive values of foods. This quality varies somewhat according to the indi- 

 vidual, so that foods which are useful to one are injurious to another. Moreover, 

 our knowledge of the degree of digestibility of any food is a matter rather of infer- 

 ence than of fact ; still, when foods are mixed as in ordinary diet, the amount of 

 imused matter in the daily supply has been ascertained with an approach to truth, 

 and suffices for comparison wlien changes of mixed foods are made. The extension 

 of this knowledge is of the highest importance in physiology, and particularly in 

 reference to those who are fed at the public expense, and whom it is a public duty 

 to feed sufficiently at the smallest cost. The problem is one very easy of solution 

 under proper conditions, and consists simply in determining, under certain typical 

 conditions, what proportion of a given food leaves the body unused. The method 

 is accurate, and not difficult of application, and of all conditions in which it could 

 be used, that of human life is probably the best, since typical men could be selected, 

 and every other condition, except that imder inquiry and the efiect of season, could 

 be kept unifonn from day to day. I am very desirous to impress this part of the 

 subject upon the public mind, for in no other way can the information which is so 

 essential to the public weal be acquired. Had the recommendation of Lord Car- 

 narvon's Committee of the House of Lords been adopted by the Government, and 

 a suitable Commission been issued, the whole question of tbe digestibility of foods 

 might have been set at rest in the course of two years. 



As to the chemical constitution of foods, there are certain leading facts relating 

 to this subject which have been under constant inquiry for some years past through- 

 out Em-ope and America, and much information has been gained. These refer to 

 the transformations of foods, and to the outlets by which they finally leave the 

 body. Thus the experiments of the late Dr. Dundas Thompson, Messrs. Lawes 

 and Gilbert, myself, and others, have, I think, proved that, whilst nitrogenous foods 

 supply the nitrogenous tissues, and ultimately leave the body chiefly as urea, they 

 have the fm-ther quality of stimulating aU vital actions, and thereby of increasing 

 the transformation of other and carbonaceous foods. The transformation of the 



8* 



