LOSS OF NITROGEN DURING FEEDING 255 



at Rothamsted in 1854 with pigs, the animals being confined in 

 a frame resting upon a sloping zinc bottom. They were watched 

 day and night during the experimental period, and the voidings 

 were collected as soon as passed, and analysed at regular 

 intervals for dry matter, ash, and nitrogen. The results were, 

 however, not satisfactory ; there was a considerable portion of 

 the nitrogen of the food unaccounted for in either the increase 

 of weight or in the excrements. The results seemed to show 

 that the loss was probably due to the difficulties of proper 

 collection and analysis of the excreta, so that the experiment 

 was repeated with greater precautions in 1862. This time the 

 losses of nitrogen were much reduced, and when allowance was 

 made for the many unavoidable sources of error, the results 

 supported the idea that the whole of the nitrogen of the food 

 not stored up as increase passed over into the manure. Other 

 experiments were made with sheep ; but again it was impossible 

 to avoid some mechanical losses, and to eliminate the uncertainty 

 due to lack of exact knowledge of the composition of the 

 animal at the beginning and close of the experiment. 



Later experiments on the Continent have indeed set the 

 point at rest, and shown that there is no decomposition of 

 nitrogenous matter of the food into nitrogen gas during the 

 vital processes, but that the whole of the digested nitrogen 

 which is not utilised for increase, milk, etc., is voided in the 

 urine. 



The practical question which greatly occupied the attention 

 of Lawes and Gilbert was that of the manure value of the 

 many purchased cattle foods commonly used in this country, 

 and particularly the compensation to be paid to an outgoing 

 tenant for their consumption in the latter years of his tenancy, 

 before he could be supposed to have obtained a return from 

 them in the shape of the crop. Lawes and Gilbert therefore 

 prepared a table showing the composition of most of the cattle 

 foods commonly in use, and calculated what proportion of the 

 nitrogen, phosphoric acid, and potash present would under 

 normal conditions be retained by fattening stock consuming the 



