GILBERT ON X.-Discourse :-On the Composition of the Animal Portion of our Food and on its Relations to Bread. BY J. H. GILBERT, Ph. D. F.C.S. (Abstract). IT has been pretty generally maintained that the comparative values of our stock-foods as such are determinable chiefly by the proportion of nitrogenous constituents which they contain. The results of experiments on the “feeding” or I‘ fattening” of animals for the purpose of human food do not bear out this conclusion. It has been further pretty generally assumed that in the admixture of animal food with our otherwise chiefly farinaceous diet the nitro- genous or so-called ‘(flesh-forming constituents,” are increased in their proportion to the more purely respiratory and fat-forming capacity of the food.It was submitted that such an explanation of the benefits derived by the admixture of our animal with our staple vegetable aliments is not admissible. The experimental data upon which the Discourse was founded had been collected by Mr. Lawes and Dr. Gilbert in the course of a lengthened inquiry,* the main objects of which had been to determine with a view to the agricultural bearings of the subject the relations of the constituents consumed in the food of fattening animals to those stored up in their bodies as increase on the one hand and to those voided as manure on the other. So far how-ever as the composition of the animals was adequately determined for the purposes of such an inquiry the results mould also afford some insight into the characters and composition of the food sup-plied to man in the bodies of the fed and slaughtered animals.The average composition of wheat-flour bread had also been carefully determined. The means of comparing with one another our staple animal and vegetable foods mere thus at command. The weights of the carcases arid of the several internal organs and other separated parts had becn determined in the case of * See “ Experimental Inquiry into the Composition of some of the Animals fed and Slaughtered as Humin I”ood.”-By J. 13. Lawes Esq. F.R.S. and J. H. Gilbert Ph. D. -Proceedings of the Royal Society) 1’01. ix. p. 348 ; and for full details- ‘‘The Transactioas of the Royal Society ” ANIMAL FOOD IN RELATION TO BREAD. several hundred animals-bullocks sheep and pigs-which were selected for slaughtering in different conditions of maturity and fatness.It appeared that whilst the internal organs-or so to speak the machinery employed in the production of the meat-- iucreased considerably in actual weight during the “feeding” or “fattening” period yet they diminished in proportional amount to the whole body or to the carcase. That is to say it was the carcase-the most important edible portion-that increased the most rapidly. To ascertain more exactly the composition of our slaughtered animals and of their increase whilst fattening 10 animals of dif- fcrent descriptions and in different conditions of maturity had been devoted. In these the amounts of water mineral matter nitrogenous substance and fat had been determined; (1) in the entire carcases; (2) in the collective “offal” parts; (3) in the entire bodies.The results showed that the largest item in the dry or solid substance of the animal bodies was fat ;and that by far thc largest proportion of that in the whole bodies was found in thc carcase parts. The carcases of well-fattened animals (those of calves excepted) appeared to consist of fat to the extent of from one-third to one-half of their entire weight. The percentage of‘ fat in both carcase and offal parts but especially in the former increased very considerably during the feeding period whilst that of the nitrogenous substance diminished. Excluding the calf the entire bodies in a condition of fatness fit for human food consisted of about one-third and sometimes of considerably more thau one- third of pure dry fat.The dry nitrogenous substance on the other hand even including that of the wool in the case of the sheep amounted to less than one-half and sometinies to less than one-third as much as the dry fat. Applying the results to calculate the composition of the increase of animals liberally fed on fattening food it appeared that this would probably consist of nearly three-fourths dry solid substance. Little less than two-thirds of the gross increase of highly fed aiiimals would be far itself; and 6 to 8 or 9 per cent. only dry nitrogenous substance. It was calculated that frequently iiot more than 5 and seldom if ever as much as 10 per cent. of tlie nit rogcnoua substance of the fattening food would be finally stored up in the increase of the animal.In some cases of experi-ments with pigs it was cstirnated that more than 4 tirncs as much fat tiad heen stored up iii the increase as had liecr supplied ready GILBERT ON formed in .the food. Three-fourths of the fat of the increase had therefore been produced from other constituents of the food. If starch were the source of this produced fat it would require about 23 parts of that substance for the production of 1 part of fat. The general conclusions mere-that but a small proportion of the increase of a fattening animal was nitrogenous substance ;that less than 10 per cent. and even as little as 5 per cent. of the nitrogenous substance of good fattening food would probably be finally stored up in the increase ; that the proportion of fat stored up was very much greater than that of nitrogenous substance; and lastly that the stored up fat would frequently involve in its production an amount of the non-nitrogenous constituents of the food much greater than the weight of the stored up fat itself.When in addition to these facts it was remembered how great would be the demands upon the non-nitrogenous constituents of the food for the maintenance of the respiratory process it need hardly excite surprise-that the comparative values of fattening foods as such seemed to be determinable more by their proportion of digestible or available non-nitrogenous than by that of their nitrogenous or assumed flesh-forming constituents.Accordingly numerous experiments with staple fattening food-stuffs Bad shown that both the rate of consumption for a given weight of animal within a given time and the amount of increase in weight pro- duced had a much closer connection with the amount of non-nitrogenous or of total dry organic constituents than with that of the nitrogenous constituents in the food supplied. This was strikingly the case when our ordinary cereal grains and leguminous seeds were compared with one another on the points in question. It remained to compare our staple animal foods (produced and composed as above described) with our most important vegetable ali- ment-bread in relation to the proportion in each of theJle,..h-form- ing to the respiratory and fat-$orrning capacity.From a careful consideration of what portions of the fattened animals would be on the average consumed it was estimated that in thc so-applied parts of oxen thcre would be from 2 to 3 timcs arid in those of lambs sheep and pigs frequently more than 4 timcs as much dry- fat as dry nitrogenous substance. According to the numerous resultsof Drs. Watson and Odling and of Mr. Lawes and Dr. Gilbert wheat-$our lweacl was reckoned to contain from 6 to 7 parts of noii-nitrogermis to 1 of iiitrogciious substancc. It might ANIMAL FOOD 1N RELATION TO BREAD. be assumed that in a certain broad yet at the same time ad- mittedly qualified sense 1part of fat was equal to 2+ parts of the starch and other non-nitrogenous matters in bread in point of respiratory and fat-forming capacity.Adopting this assumption it appeared that in the consumed portions of well-fattened oxen the relation of the respiratory and fat-forming to the flesh-forming capacity would be about the same and in those of well-fattened lambs sheep and pigs about 1+ times as high as in the staple vegetable food-wheat-$our bread. Were it granted that the pro- portion of the whole fat of the slaughtered animals which was sup-posed to be consumed was too high it must on the other hand be remembered that the nitrogenous substance would contain a con- siderable proportion of gelatigenous matter the applicability of which for flesh-forming mas to say the least doubted. It ap-peared therefore so far as chemical inquiry of the kind in ques- tion was competent to throw light on the point that on the large scale the introduction of animal aliments into our otherwise chiefly farinaceous diet did not increase but diminish the relation of the so-called flesh-forming to the respiratory and fat-forming capacity of the collective food. It remained then for physiology yet to providc the true explanation of the admitted benefits arising from thc admixture of animal food with bread.