PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 647 



Name of food. Weight in lb. Price per lb. Cost. 



Bread 2.345 2 4f 



Lean ham, boiled 3.001 16 4 6 



Mackerel 3.L24 8 2 1 



LeanbeGf.- 3.522 10 3 6i 



Lean veal 4.300 10 4 3-i 



Potatoes _. 5.068 1 &i 



Milk 8.021 (5d. per quart.) 1 3i 



White of egg-- 8.745 6 4 4^ 



Carrots 9.685 li 1 ^ 



Cabbage 12.020 1 10^ 



Pale ale, bottled _ 9 bottles, 10 7 6 



At London, the relative cheapness of the principal artices of 

 food, is represented by the following order, viz : Oatmeal, flour, 

 pea-meal, bread, potatoes, ground rice, beef-f;it, grape sugar, 

 cabbage, cheese, butter, eggs, carrots, cane sugar, milk, mackerel, 

 beef, veal, and lastly, pale ale, which, as a motor, costs twenty -four 

 times more than flour. 



Source of Muscular Power. 

 Liebig and his disciples have held that, while animal heat is the 

 result of oxydation of food, animal energy is due to the oxyda- 

 tion of muscle. Dr. Mayer in 1842 determined the mechanical 

 eqivalent of heat, and soon after took exception to the doctrine of 

 Liebig regarding the cause of muscular power. As early as 1845 

 he maintained that a muscle is only an apparatus by means of 

 which the transformation of force is effected, but it is not the 

 material by the change of which mechanical work is produced. 

 The fire-place in which this combustion goes on is in the interior of 

 the blood-vessels and blood, however- — a slowly-burning liquid — 

 being the oil in the lamp of life. Every motion in an animal is 

 attended by the consumption of oxygen and the production of 

 carbonic acid and water ; every muscle to which atmospheric oxy- 

 gen does not gain access ceases to perform its functions. In other 

 words, Mayer maintained that the chemical change developing 

 force, was in the capillaries of the muscle. Quite recently Pro- 

 fessor Franklaud, of Loudon, has thrown new light on this subject 

 by ascertaining the amount of force generated by the oxydation 

 of a given quantity of muscle, also the quantity of muscle oxy- 

 dized in the body while the muscles are exerting a given amount 

 of mechanical force ; thus showing very clearly that the muscle 

 by oxydation could not furnish one-fifth of the actual force exerted. 

 In calculating the amount of force generated in a given time by 



