340 



THE ROTHAMSTED EXPERIMENTS. 



Liebig's 

 view not 

 confirmed. 



The result was, then, that with exactly equal conditions as 

 to exercise, both animals being in fact at rest, the amount of 

 urea passed by the one feeding on the highly nitrogenous 

 lentil-meal was, in each case, more than twice as great as 

 that voided by the one fed on the barley-meal, supplying less 

 than half the amount of nitrogen. 



It was clear, therefore, that the rule laid down by Liebig, 

 and so long generally adopted by others, did not hold good, 

 namely, that — " The sum of the mechanical effects produced in 

 two individuals in the same temperature is proportional to the 

 amount of nitrogen in their urine; whether the mechanical 

 force has been employed in voluntary or involuntary motions, 

 whether it has been consumed by the limbs or by the heart 

 and other viscera " — unless, indeed, as has been assumed by 

 some experimenters, that there is, with an increase of nitro- 

 genous substance in the food, an increased amount of mecha- 

 nical force employed in the " involuntary motions " sufficient 

 to account for the increased amount of urea voided. 



It was at any rate obvious that, if the amount of urea 

 voided by one animal at rest could be more than twice as 

 great as that voided by a similar animal also at rest, and 

 under otherwise equal conditions, provided only that the food 

 of the one contained more than twice as much nitrogen as 

 that of the other, the amount of urea passed could not be any 

 measure of the amount of muscular power exerted. 



The subject was taken up again at Eothamsted in 1862, 

 arid accordant results were obtained as follows : — 



Later 



trials. 



TABLE 77, 



-Experiments at Eothamsted with Pigs. 

 August-September 1862. 



Quantities per head per day. 



Dr E. 



Smith's 

 trials. 



Not long after the publication of our views in 1852, and 

 the experiments with pigs in 1854, with the results of which 

 he was acquainted, the late Dr Edward Smith instituted ex- 

 periments to determine the amounts of carbonic acid exhaled 

 in respiration under various conditions as to muscular exer- 

 cise. His results were published in a paper presented to the 



