310 



THE KOTHAMSTED EXPERIMENTS. 



A mount of 

 fat produc- 

 ible from 

 nitrogen in 

 mangels 

 uncertain. 



A large 

 proportion 

 of increase 

 derived 

 from carbo- 

 hydrates. 



Nitrogen 

 in clover- 



high, in nitrogen, and doubtless containing a larger proportion 

 of their nitrogen as non-albuminoid compounds. 



From these various considerations it is obvious that by no 

 means the whole of the nitrogen of the mangels can be 

 estimated as having existed in compounds which could, in 

 their transformation, yield the amount of fat possibly deriv- 

 able from true albuminoids. However, with the great varia- 

 tion in the proportion of albuminoids and amides in roots, 

 and the absence of exact knowledge as to the probable value, 

 if any, direct or indirect, of amides for fat-formation, it is 

 impossible to form any certain estimate as to which of the 

 percentages given alternatively in the lower division of the 

 table most probably represents the amount of fat producible 

 from the nitrogenous substance of the mangels given ad 

 libitum in each of the five pens of the first series of experi- 

 ments with sheep. It is, however, quite safe to conclude 

 that very much less than the whole would be so available ; 

 and if we were to assume that of the nitrogenous constituents 

 of the roots only the albuminoids would be available for fat- 

 formation, the figures given in the top line of the lower 

 division of the table, according to which it is reckoned that 

 only 50 per cent of the total nitrogenous compounds of the 

 roots would be capable of fat-formation, would in each case 

 represent less than half the amount required. 



It is quite clear that, at any rate a large proportion of the 

 increase estimated to be necessarily derived from other 

 sources than the fat of the total food, and the nitrogenous 

 substance of the fixed food, must have been derived from 

 other sources than the nitrogenous substance of the roots ; in 

 other words, it must have had its source in the carbohydrates 

 of the fixed food or of the roots. 



Let us now examine the evidence of the results of the second 

 series of experiments, on somewhat similar lines. 



As in Series 1, a fixed quantity of barley or malt was given 

 in each pen, but now a fixed quantity of clover-chaff also. 

 This introduction of clover-chaff into the fixed food brings us 

 again face to face with the difficulty as to the estimation of 

 the food-value of the amides. As already said, the calculation 

 of the amounts of the nitrogenous substance in the clover- 

 chaff which will be available are made on the assumption 

 that 66.7 per cent of the total nitrogen will be digestible, 

 and so available; and this figure agrees fairly with Wolff's 

 estimates. But this amount includes amides as well as 

 albuminoids. In "Wolff's most recent tables he estimates 

 that the proportion of the nitrogen of clover-hay existing in 

 non-albuminoid compounds may range from 13.9 to 29.9 per 

 cent of the whole, and probably be on the average about 19 



