384 THE POPULAR SCIENCE MONTHLY. 



not only from the light thrown on many of the obscure processes of 

 nutrition, but also in laying a foundation for a consistent system of 

 feeding, in which the relations of the food consumed to the special 

 animal products obtained, and to the value of the manure produced, 

 as an incident of the process, are clearly traced. 



In determining the amount of food and of its several constituents 

 consumed for a given live weight of the animal in a given time, aud 

 the amount of food and of its several constituents required to produce 

 a given amount of increase in live weight, several hundred animals, 

 including oxen, sheep, and pigs, were subjected to experiment. In 

 these researches, selected lots of animals were supplied, for weeks or 

 months, with weighed quantities of food of known composition, as de- 

 termined by analysis, and especially adapted to the particular point 

 under investigation. The animals were weighed at the beginning, at 

 intervals during the progress, and at the close of the experiment. 



The composition of the manure produced from a given amount and 

 quality of food consumed, by oxen, sheep, and pigs, was determined 

 in a large number of cases by analyzing average samples of the food, 

 and then making an analysis of the solid and liquid excretions of the 

 animals. In these experiments, the oxen were fed in boxes in which 

 the manure was preserved with litter of known composition. After 

 feeding for from five to nine weeks, the total manure produced was 

 carefully mixed, weighed, sampled, and analyzed. By this method 

 the solid and the liquid exci-eta were not separately examined. With 

 sheep no litter was used, the animals, in lots of five, being fed on a 

 slatted platform with an inclined floor of sheet-zinc below it, so that 

 the urine was drained into carboys containing acid, while the solid 

 excretions were separately removed several times a day and preserved 

 for analysis. The constituents determined in the food and in the ma- 

 nure in the experiments with oxen and sheep were dry matter, mineral 

 constituents, and nitrogen, and in some cases woody fiber. As an 

 illustration of some of the difficulties that must be overcome in mak- 

 ing exact investigations of this kind, a more particular description of 

 some of the devices resorted to will be of interest. " In the case of 

 pigs, individual male animals were experimented upon, each for pe- 

 riods of three, five, or ten days only. Each animal was kept in a 

 frame, which prevented it from turning around, and having a zinc 

 bottom, with an outlet for the liquid to run into a bottle, and it was 

 watched night and day, and the voidings carefully collected as soon as 

 passed, which could easily be done, as the animal never passed either 

 fseces or urine without getting up, and in getting up he rang a bell 

 and so attracted the notice of the attendant. The constituents de- 

 termined were, in the food and fseces, dry matter, ash, and nitrogen, 

 and in the urine, dry matter, ash, nitrogen, and urea." 



The amount and relative proportion of the different organs and 

 parts of the body were determined in two hundred and forty-nine 



