No. 85. j 211 



tions were not interrupted ; because the attraction at the ends of the 

 sections is weakened by the increased distance. If the chasms were 

 filled by the deposition of new particles from the blood, the same 

 effort with equal energy may be repeated ; and if the blood were an 

 exhaustless reservoir, the nitrogenized compounds might be as con- 

 stantly supplied to the wasting tissues, as muscular effort should re- 

 quire. But at the close of the digestion of a meal, the supply of ni- 

 trogenized compounds is in a measure arrested ; and the quantity in 

 the blood, being a fixed quantity, determined by the kind and amount 

 of food eaten, will in process of time be exhausted. The inability to 

 muscular effort arises from consumption of muscular fibre, and ex- 

 haustion of nitrogenized constituents of the blood. The fatigue is the 

 natural pain which accompanies this condition of a muscle. 



This explanation, though gross in comparison with the delicate and 

 elaborate processes constantly going on among the organic tissues, 

 may not be altogether without service in enabling us to comprehend 

 the demand which labor makes upon the nitrogenized and other com- 

 pounds — makes upon food which contains these essentials. Other 

 organized substances are expended in labor, and must be replaced 

 through the blood from the food, such as the earthy matters of which 

 bone is composed. 



Some kinds of food contain these essentials in larger quantities than 

 others, and will therefore be more profitably grown and consumed. 



II. It is also well known that cattle and sheep fatten more rapidly 

 upon some substances than upon others, and that the food which will 

 sustain much physical labor, is not necessarily the food that will fat- 

 ten most expeditiously. 



To know what kinds of food will most advantageously increase the 

 flesh, the mere fat of stock designed for slaughter, and what admix- 

 tures of the two kinds of food are best adapted to sustain a good coat 

 of flesh, and yet permit vigorous service, is obviously of no small im- 

 portance. 



Prout, anxious to know what kinds of food, and what proportions 

 of those kinds were best adapted to the physical development of ani- 

 mals, commenced his investigations by an analysis of the human 

 milk. He found it consisted of three substances dissolved in water ; 

 one of these containing nitrogen, and the other two destitute of nitro- 



The nitrogenized substance is called caseine, and is the basis of 

 cheese. The other two substances were sugar of milk and oil. 



The oil is separated from the other two by agitation, and the par- 

 ticles aggregate in the form of butter. 



The sugar gives the sweetness to new milk, and in the fermenta- 

 tion which succeeds, gives rise to the acid principles observed in milk 

 after standing a day or two. 



The caseine or basis of cheese being the only organic principle that 

 could form muscle or tissue of any kind, because the only one that 

 contains nitrogen, the other two substances mu^t have another office 

 to perform. 



The oil of the milk is deposited in the form of fat, around the mus- 



