308 



THE EOTHAMSTED EXPERIMENTS. 



Nitrogen- 

 ous sub- 

 stance 

 available. 



Fat avail- 

 able. 



True al- 

 buminoid 

 nitrogen in 

 mangels. 



Amides 

 and ni- 

 trates in 

 mangels. 



probably fully as fat as, if not fatter than, the sheep which 

 had been analysed as "fat." Taking into account the weight 

 and condition of the animals at the beginning and at the end, 

 and the percentages of carcass and of inside fat in the live- 

 weight, it is calculated that the increase over this short finish- 

 ing period would contain 74 per cent of fat, and only 6.5 per 

 cent of nitrogenous substance. 



On these assumptions the figures show that, after deduct- 

 ing the estimated amount of nitrogenous substance in 100 of 

 increase from the amount supplied in the fixed food, there 

 remained in the different cases — 18.5, 16.8, 13.4, 18.5, and 

 21.4 parts, of nitrogenous substance available from the fixed 

 foods for the formation of fat. 



Next as to the fat : — deducting the amount of the digestible 

 fat supplied in the total food from the fat in the increase, 

 there remain in the respective cases 63.7, 65.2, 64.4, 63.7, 

 and 63.8 parts, which must have been newly-formed. There 

 is next shown the amount of this which may have been de- 

 rived from the available nitrogenous substance of the fixed 

 food ; and it is seen that there remain — 54.2, 56.6, 57.5, 

 54.2, and 52.8 parts, out of the total of 74 in the 100 of 

 increase, that must have been derived from other sources — in 

 fact, either from the nitrogenous substance of the roots, or 

 from the carbohydrates of the fixed food and the roots. 



The next question is, whether the nitrogenous substance of 

 the roots could have yielded the amounts of fat indicated to 

 have been produced from other sources than the fat of the 

 total food, and that derivable from the available nitrogenous 

 substance of the fixed foods. Comparing the figures in the 

 bottom line of the lower division of the table with those in 

 the bottom line of the upper division, it is seen that, even on 

 the impossible assumption that the whole of the nitrogen of 

 the mangels existed in compounds of the same fat-forming 

 value as the albuminoids, in neither of the five cases would 

 the amount so available completely supply the amount 

 required. 



The amount of true albuminoid nitrogen varies very much 

 in different descriptions of roots, and in the same description 

 according to season, maturity, &c. Thus, at Eothamsted we 

 have found it in mangels as low as 20.5 per cent of the total 

 nitrogen under unfavourable conditions of growth and ripen- 

 ing, and as high as 44.2 under favourable conditions. We 

 generally assume in calculation that 40 per cent of the 

 nitrogen of mangels will, on the average, exist as albumin- 

 oids ; and Wolffs average figure, as given in 1888, is 36.1 

 per cent. The amount existing as amides wall probably in 

 most cases vary from 40 to 50 per cent or more, whilst there 



