FEEDING OF ANIMALS. 337 



Food and the Exercise of Force. 



We now come to the last branch of our subject — namely, 

 The Feeding of Animals for the Exercise of Force. With the 

 very limited space still left at our disposal, we will commence 

 our historical sketch with a brief account of the views of 

 Liebig as first put forward in 1842 in his work On Organic Liebig's 

 Chemistry in its applications to Physiology and Pathology. mews - 

 There is, indeed, a special appropriateness in so doing, since 

 there can be no doubt that the course of subsequent inquiry 

 and discussion has been materially influenced by the opinions 

 he then enunciated. 



The following quotations from the above-mentioned work 

 will suffice to indicate his more specific views in regard to 

 the connection between food requirements and the exercise 

 of force : — 



As an immediate effect of the manifestation of mechanical force, we 

 see that a part of the muscular substance loses its vital properties, its 

 character of life ; that this portion separates from the living part, and 

 loses its capacity of growth and its power of resistance. We find that 

 this change of properties is accompanied by the entrance of a foreign 

 body (oxygen) into the composition of the muscular fibre (just as the 

 acid lost its chemical character by combining with zinc) ; and all ex- 

 perience proves, that this conversion of living muscular fibre into com- 

 pounds destitute of vitality is accelerated or retarded according to the 

 amount of force employed to produce motion. Nay, it may safely be 

 affirmed that they are mutually proportional ; that a rapid transfor- 

 mation of muscular fibre, or, as it may be called, a rapid change of 

 matter, determines a greater amount of mechanical force ; and con- 

 versely, that a greater amount of mechanical motion (of mechanical 

 force expended in motion) determines a more rapid change of matter. 

 —Pp. 220, 221. 



And again : — 



The amount of azotised food necessary to restore the equilibrium 

 between waste and supply is directly proportional to the amount of 

 tissues metamorphosed. 



The amount of living matter, which in the body loses the condition 

 of life, is, in equal temperatures, directly proportional to the mechanical 

 effects produced in a given time. 



The amount of tissue metamorphosed in a given time may be 

 measured by the quantity of nitrogen in the urine. 



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. — Ibid., p. 245. 



Such, in fact, were the views in regard to the special 

 exigencies of the system in the exercise of force, which be- 

 came at once identified with Liebig's name, and continued to 



VOL. VII. Y 



