GOOD FOOD. 
19 
nitrogen does not exist in these substances in large quantities^ 
but it is a distinguishing ingredient. We have seen that two 
substances exist in the body called fibrine and albumen^ the 
former entering into the composition of the muscles^ the latter 
that of the nerves. Now these substances are contained in 
our vegetable food^ and it appears that they are directly con- 
veyed from the vegetable to the animal. We have no know- 
ledge of any power in the animal system to manufacture 
these substances. All the nitrogen which is contained in an 
animal is derived from the vegetable kingdom. It is the 
peculiar property of the plant to be able_, in the minute cells of 
which it is composed^ to convert the carbonic acid and ammonia 
which it gets from the atmosphere into fibrine and albumen. 
By easy chemical processes we can separate these substances 
from our vegetable food. Wheats barley^ oats_, rye^ rice_, all 
contain fibrine_, some of them also albumen. Potatoes^ cab- 
bages_, and asparagus contain albumen. It is a well-ascertained 
fact that those substances which contain most of these nutri- 
tious secretions as they have been called_, support life the 
longest. Liebig calls them flesh formers. They undergo 
little change during digestion_, and present themselves in a 
pure state in the bloody where they are directly employed in 
the renewal of nervous and muscular matter. They are the 
agents which renew the thinking and working powers of 
man. They are probably destroyed at the same moment 
that the carbon is converted into carbouic acid gas^ 
but in their last stage they pass off from the body in the 
form of urea. The nitrogen lost in the destruction of the 
fibrine and the albumen is found in the nitrogen of the urea. 
Mere existence is represented by the loss of carbonic acid^ but 
the work of the system in its thought and its muscular labour 
is represented by the nitrogen of the urea. Nor is this the 
mere dream of the theorist : it has been practically demon- 
strated that increased stress upon the nervous system^ viz.^ 
brain- work^ emotion^ or excitement from disease^ increases the 
quantity of urea and the demand for nitrogenous food. In the 
same manner the amount of urea thrown off is the representa- 
tion of the amount of muscular work done. 
Important as these two groups of food are^ they do not 
exhaust all that is necessary to constitute good food.'’"’ In 
addition to the compounds of the four organic elements_, the 
human body requires certain saline constituents^, without which 
it cannot exist. These are the five pounds of phosphate of 
lime_, the pound of carbonate of lime^ the three ounces of 
fluoride of calcium^ the three ounces and a half of common 
salL with the other salts. They are all passing off from the 
body at the rate of about one ounce in the twenty-four hours. 
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