EARLY THEORIES OF M'TIMTIoN -JH 



values " may 1)6 instanced ; in ls()«> lie puLlislicd a ial)l.' ot all 

 the recognised cattle foods, ranged in order and marked lo slntw 

 how much of each was equivaliMit to 100 parts of hay taken a> 

 a standard. Timer's hay values were Itascd parhv on liis own 

 experience as a practical man and partly on attempts, very 

 imperfect in the then state of ehemieal kiiowlrd^p, to estimate 

 by analysis the nutritive constituents of the foods, liou.ssiniiault's 

 investigations were the earliest serious attempts to apply .scien- 

 tific principles to the feeding of animals ; the importance of the 

 nitrogenous constituents of food had now become clear, so his 

 first work consisted in determining the proportion of nitrogen 

 present in a large numljer of feeding materials. C'areful 

 practical trials were then made with a few selected foods, and 

 as a result he published a revised table of hay values, ])ased on 

 the amount of nitrogen the foods contained, and checke(l to 

 some extent by his practical experience. His experiments led 

 Boussingault to bring into prominence the non-nitrogenous 

 constituents of food, but in general his conclusions were that 

 the comparative values of food-stuffs are determined rather by 

 their nitrogenous than by their non-nitrogenous constituents. 

 In this subject Boussingault's was the pioneer work, and 

 Liebig, who in many respects must be regarded as the 

 originator of any general theory of animal nutrition, in the 

 main arrived at his deductions fi'om Boussingault's results. 

 Liebig also, and perhaps even more strongly than Boussingault, 

 looked at the nitrogenous matter as the most im])ortant 

 con.stituent of food for the production of both increase and ••!" 

 work. 



In this position was the science of animal nutrition uln'ii 

 Lawes and Gilbert began their experiments on fce(lin<:. .nid 

 natm-ally the direction their experiments took was maiidy 

 determined by the views then prevailing. The most notable 

 characteristic of the Rothamsted experiments on animals was 

 that from the first they were concerned with animals increasing 

 in weight rather than with animals whose food rations wen- 

 adjusted to maintain them in a ccaistant condition. Ihr 



