NUTRIENT VALUE OF FOOD. 399 



The nutrient quality of any one substance depends upon the inter- 

 vention of some other body ; and it is only by the reciprocal action of 

 these four fundamental substances that life can be maintained, even 

 as it was originally begun and influenced by the same means. We 

 ought, therefore, to distinguish, in our consideration of the absorp- 

 tion of matter necessary for the maintenance of life, between those 

 essential nutrient matterswhich we have learnt to know as adjunctsin 

 the metamorphosis of matter and those articles of food, which origi- 

 nating either in the vegetable or animal kingdom, generally contain 

 the former in combinations of the most varied proportions. This 

 is, however, so obvious, that after what has been already advanced, 

 it would be superfluous to enter further into the subject But 

 if the various articles of food differ to so extraordinary a degree 

 in the amount of nutrient matters belonging to these four groups, it 

 would not seem out of place to estimate the value of food by the pro- 

 portion in which these substances are combined in them, so as best 

 to promote nutrition. However justly the albuminous matters may 

 be termed histogenetic or organo-plastic, and however indispen- 

 sable they may be to the vital organs, we must necessarily ascribe 

 a very limited nutritive force to all articles of food which in addi- 

 tion to the albuminates contain neither fats nor carbo-hydrates, arid 

 even if all these matters were combined together in one article of 

 food, we could scarcely ascribe to it any great degree of nutrient 

 force, unless there were also phosphates and other salts present in 

 it, for no cell or fibre could be formed or regenerated without the 

 co-operation of these salts. If, therefore, all four groups of nutrient 

 substances are equally necessary to afford compensation to the animal 

 organism for the matters which have become effete, or to supply 

 materials for the establishment of new manifestations of force, 

 those articles of food will be the best and the most invigorating 

 which consist of such substances combined in the proportion which 

 is best adapted to the animal organism. Hence we see, that the 

 idea of the nutritive value of any article of food is entirely relative, 

 as it depends partly upon the proportion in which the four funda- 

 mental bases of nutrition are mixed in it, and partly upon 

 the individual requirements of the organism that is to be 

 nourished. 



There are, therefore, two points which specially demand our 

 attention in entering upon a scientific consideration of food 

 generally, and of its nutritive qualities specially ; the first refers to 

 the amount of these four elements, which it contains ; and the 

 second, to the circumstances under which the organism exhibits a 



