Economical Value of Food. 53 



the animal, and the more we facilitate the assimilation of food, 

 the more rapidly it will become fat. By steaming, likewise, the 

 disagreeable smell of musty hay or cake is destroyed, and on the 

 whole, steamed food becomes more palatable. 



6. On small Proportions of Substances with which ice may not 

 even be acquainted. Professor Liebig's researches on the juices of 

 flesh have made us acquainted with a remarkable crystallized 

 substance, to which he has given the name Kreatine. This sub- 

 stance appears to exercise a remarkable "function in the digestion 

 of food. Liebig also showed the presence of phosphate of potash 

 and lactic acid in the juice of flesh, and considers these consti- 

 tuents indispensable for the digestion of meat. He has indeed 

 proved that flesh, from which all juice is perfectly extracted by 

 water, is so indigestible, that even dogs will refuse to eat it. 



The total amount of the compounds which appear to play so 

 important a function in the digestion of meat is but very small. 

 Now, if the digestibility of flesh is determined in a great measure 

 by small quantities of substances, the importance of which re- 

 mained unnoticed until the master researches of a Liebig on the 

 juices of flesh made us acquainted with the influence the above- 

 mentioned substances play in the process of digestion is it not 

 likely that vegetable food may contain small quantities of com- 

 pounds which exercise a similar influence ? 



In conclusion it may be observed, that the economical value 

 of food is further influenced 



1. By prejudicial substances which food may contain. Thus, for 

 instance, mustard cake cannot be used as a feeding material, 

 notwithstanding its containing a large amount of flesh-forming 

 and fat-producing substances, because in the stomach of the 

 animal fed upon it, it gives rise to the production of the poison- 

 ous irritating essential oil of mustard : or, the refuse cake, pro- 

 duced in the manufacture of castor oil, cannot be used for 

 feeding purposes on account of the drastic effects which the oil, 

 still remaining in the cake, will produce in the animal system. 



2. By the mechanical effect the food exercises. An illustration 

 in point is offered in bran, which, on account of its sharp edges, 

 stimulates the nerves of the digestive canals to such an extent 

 that much of it passes through the system undigested. Other- 

 wise bran ought to be very nutritious, for it contains even more 

 flesh-forming matters, as well as more fatty matter, than wheaten 

 flour. Could not these relaxing effects of bran which, I believe, 

 are principally due to its mechanical condition, be overcome by 

 the cooking or steaming of the bran ? 



3. By the physical condition of the food. It is so self-evident 

 that mouldy, fusty food cannot be so good as it is in a fresh state, 

 that I need not dwell on this point. Every one knows that the 



