524 



NATURE 



\Sept. 30, 1880 



chemist takes the various vegetable products in the condition in 

 which they are used on the farm, or sold from it. And as a 

 very large proportion of what is grown, such as grass, hay, roots, 

 tubers, and various green crops, are not matured productions, it 

 comes to be a matter of great importance to consider whether or 

 not any large proportion of the nitrogenous contents of such 

 products is in such condition as not to be of avail to the animals 

 which consume tliem in their food? 



We cannot say that the wliole of the nitrogen in the seeds 

 witli which we have to deal exists as albuminoids. But we may 

 safely assume that the nearer tliey approach to perfect ripeness 

 the less of non-albuminoid nitrogenous matters will they con- 

 tain ; and in the case of the cereal grains at any rate, it is pro- 

 bable that if really perfectly ripe they will contain very nearly 

 the whole of tlieir nitrogen as albuminoids. With regard to 

 some leguminous and other seeds, ^^hich contain peculiar nitro- 

 genous bodies, the range may however be wider. 



But whatever the condition of the nitrogenous bodies in the 

 seeds we grow or sow, with germination begins a material 

 cliange. Albuminoids are transformed into peptones, or pep- 

 tonelike bodies, or degraded into various aiiido- or other 

 compounds. Such change into more soluble and more diffu- 

 sible bodies is, it is to be supposed, essential to their free 

 migration, and to their subserviency to the purposes of growth. 

 In the case of the germination, especially of some leguminous 

 seeds, asparagine has been found to be a very prominent product 

 of such degradation of the albuminoids ; but it would seem that 

 this disappears as the green parts are developed. But now the 

 plant begins to receive supplies of nitrogen from the soil, as 

 nitrates or ammonia, and it would seem that amides constitute a 

 considerable proportion of the produced nitrogenous bodies, 

 apparently as an intermediate stage in the formation of albu- 

 minoids. At any rate, such bodies are found to exist largely in 

 tlie immature plant ; whilst the amount of them diminishes as 

 the plant, or its various parts, approacli to maturity. 



But not only have we thus, in unripened vegetable productions, 

 a greater or less, and sometimes a very large, proportion of the 

 nitrogenous bodies formed witliin Ihe plant, existing as amido- 

 conipounds, but we may have a large amount existing in the 

 juices as nitric acid, and some as ammonia, &c. Thus, E. 

 Schuize determined the nitric acid in various "roots; "and he 

 found that, in some mangels, more than one-third of the total 

 nitrogen existed in that form, and about one-tenth as much as 

 ammonia. In a considerable series at Rothamsted, we have 

 found an extremely variable proportion existing as nitric acid, 

 according to the size, succulence, or degree of maturity, of the 

 roots ; the amount being, as a rule, the least with the ripest and 

 le-s highly nitrogenous roots, and tlie most with the most succulent, 

 unripe, and highly nitrogenous ones. In some cases it reached as 

 much as from 20 to nearly 30 percent, of the total nitrogen. In 

 many other immature vegetable products nitric acid and ammonia 

 have been found ; but, so far as I remember, in none in anything 

 like so large a proportion as in the so-called "root-crops," 

 especially mangels. In many, however, the quantity appears to 

 be immaterial ; and it is remarkable that whilst there. is so much 

 in the "roots," little or none is found in potatoes. 



No wonder that,? in the experiments already referred to, we 

 found the feeding result to be the worse the more succulent and 

 immature the roots, and the higher their percentage of nitrogen, 

 accordingly. 



But it is to the difference in amount of the albuminoid bodies 

 themselves, in different descriptions of vegetable produce, that I 

 wish specially to direct attention, making, however, some 

 reference to what is known of the proportion of the nitrogen 

 existing as amido-compounds. 



In some mangels E. .Schuize found only from about 20 to 22 

 per cent, of their total nitrogen to exist as insoluble and soluble 

 albumin. But he found in one case 32-5, and in the other 40-S 

 per cent, of the total nitrogen as amides. In a large series of 

 determinations at Rothamsted, by Church's method, we. found a 

 variation of from under 20 to over 40 per cent, of the total 

 nitrogen of mangels to exict as albuminuids; or, in other words, 

 from nearly 60 to over So per cent, of it in the non-albuminoid 

 condition-. 



In potatoes Schuize found from under 50 to 65 per cent, of 

 the total nitrogen as soluble and insoluble albumin, and from 

 277 to 49'i per cent, as neutral and acid amides. In a series of 

 potatoes grown at Rothamsted, under very various conditions as 

 to manuring, and in two different seasons, we found the nitrogen 

 as albuminoids to range from little over 50 to more than 71 



per cent, of the total nitrogen, leaving, of course, from less than 

 30 to nearly 50 per cent, to be accounted for in other ways. 



Kellner determined the amount of nitrogen as albuminoids, 

 and as amido-compounds, in a considerable series of green foods, 

 both leguminous and gramineous, cut at different stages of their 

 growth. The proportion of the total nitrogen not as albuminoids 

 was, upon the whole, greater in the leguminosK: than in the 

 graminecc. In both, however, the proportion as albuminoids 

 increased as the plants approached to maturity. The proportion 

 as albuminoids was in all these products very much larger than 

 in roots, and generally larger than in potatoes. In the case of 

 first-crop meadon-hay we found in the separated gramineous 

 herbage 76"4, in the leguminous herbage S2, and in the miscel- 

 laneous herbage So '3 per cent, of the nitrogen as albuminoids ; 

 and in the second cropS6'2 percent, in the gi-amineons, 88'3 

 per cent, in the legnminous, and SS'I per cent, in the miscel- 

 laneous herbage. How far the higher proportion of the nitrogen 

 as albuminoids in the second crops is to be taken as any indica- 

 tion of the characteristics of the autumn growth, or how far it is 

 to be attributed to the accidental condition of jthe weather, may 

 be a question. 



These illustrations are sufficient to give some idea of the range 

 and proportion of the nitrogen in different feeding crops which 

 does not exist as albuminoids ; and they are sufficient to show 

 that a very large proportion of the ncn-albuminoid matter exists 

 as various amido-compounds. The question arises, therefore, 

 whether these bodies contribute in any way to the nutrition of the 

 animals which feed upon them ? We have but little experi- 

 mental evidence on this point. As green herbage is the natural 

 food of many descriptions of animal, we might suppose that 

 characteristic constituents of it would not be without some value 

 as food ; but the cultivated root crops are much more artificial 

 productions, and it is in them that we find such a very large pro- 

 portion of non-albuminoid nitrogen. With respect to some of 

 the amido compounds, at any rate, direct experiments seem to 

 show that they are digested in the animal body, and increase the 

 elimination of urea. Weiske and Schrodt found that rabbits 

 receiving, as their only nitrogenous food, either asparagine or 

 gelatin, wasted and died ; but a rabbit receiving both asparagine 

 and gelatin increased in weight and survived to the end of the 

 experiment, which lasted seventy-two days. From the results of 

 other experiments made with sheep, they concluded that both 

 asparagine and gelatin protect the albuminoids of the body from 

 oxidation. 



These considerations lead me, in conclusion, to refer briefly, 

 and I promise it shall be as briefly as is consistent with clearness, 

 to the two veiy much disputed questions of the origin of muscular 

 power, and the sources of the Jat of the animal body. These sub- 

 jects Mr. Lawes and myself have frequently discussed else^vhere_; 

 but as the controversy has assumed a new pliase quite recently it 

 seems desirable and appropriate that I should recur to it on the 

 present occasion. 



With regard to the question of the sources in the food of the 

 fat of the animal body, Liebig originally maintained that 

 although fat might be formed from the nitrogenous compounds 

 within the body, the main source of it in the herbivora was the 

 carbohydrates. In his later writings he sharply criticised the 

 experiments and arguments of those who have maintained the 

 formation of fat chiefly from the proteine compounds, but he at 

 the same time seems to attach more importance to that source 

 than he formerly did. He gives it as his opinion that the ques- 

 tion cannot be settled by experiments with herbivora. He adds 

 that what we know with certainty is that, with these animals, 

 albuminates and carbohydrates work together to produce fat ; 

 but whether the non-nitrogenous product, fat, has its origin in 

 the albumin or in the carbohydrate he considers it not easy to 

 determine. 



At the time when we commenced our experiments on the 

 feeding of .animals in 1S47 the question whether the fat of the 

 animals fed for human food was mainly derived from albuminoids 

 or from carbohydrates had been scarcely raised, or at least it was 

 not prominent. The question then was rather — whether the 

 herbivora received their fat ready formed in their food, ^ or 

 whether it was produced within the body — the latler view being 

 that which Liebig had so forcibly urged, at the same time main- 

 taining that at any rate its chief source was the carbohydrates. 

 Accordingly our experiments were not specially arranged to de- 

 termine whether or not the whole of the fat produced could or 

 could not be derived from the albuminoids. 



For each description of animal, oxen, sheep, and pigs, such 



