642 Dietaries of Labouring Prisoners in Indian Jails. [part iv. 



derived from the vegetable kingdom, seeing that, more or less directly, herbivorons 

 animals constitute the prey of the carnivora. As organised food substances usually 

 contain the requisite proportion of the unorganised, it seems unnecessary, in a note of 

 this kind, to give in detail the amount of the inorganic constituents of individual diet 

 scales. 



3. It will, therefore, be necessary to consider specially the leading characteristics 

 of organised food stuffs. These may be classified under two principal headings — those 

 which contain nitrogen and those which do not. The nitrogenous group of compounds 

 is very commonly referred to as albuminates [also proteids] from the circumstance 

 that albumen forms the most important alimentary constituent of the group — a sub- 

 stance which is directly derivable both from animals and plants. The non-nitrogenous 

 group is ordinarily sub-divided into (a) carbo-hydrates, the most important compounds 

 of which are starch and sugar ; (6) fats. 



4. In the present memorandum the sum of the ingredients in all the principal 

 scales of diet given in the text will be found resolved into these three great alimen- 

 tary principles ; but for the sake of conciseness, and as tending to simplicity of 

 arrangement, the nutritive value of the individual ingredients given in the series of 

 the appended dietary tables has been expressed in terms of nitrogen and carbon only. 

 This does not imply that these two elements are assimilated when in an uncombined 

 condition, but that the quantities of the special ingredients cited in any particular 

 diet may, in the laboratory, be resolved into so many grains of nitrogen and carbon. 

 Computations of the amount of these two elements in the different alimentary sub- 

 stances furnish a convenient and simple index of the approximate nutritive value of 

 a combination of food stuffs, seeing that, as the late Dr. Parkes expressed it, " the 

 phenomena of nutrition are chiefly owing to the various chemical interchanges of 

 nitrogen and carbon (and in some instances of hydrogen with oxygen)." 



5. Speaking generally, the chief functions of the nitrogenous principles of food 

 seem to be the development and renovation of the tissues, and the acceleration of the 

 chemical changes which take place in them ; whilst the non-nitrogenous, or carbon- 



, aceous, material furnishes the principal source of mechanical force ; or, as Pavy has it, 

 the former may be spoken of as holding the position of the instmment of action, 

 while the other supplies the motive power. The quantity and the proportions of these 

 proximate alimentary substances which are required to maintain individuals in health, 

 the particular part which each proximate aliment plays in the animal economy, and 

 the relative proportions in which they should be given during periods of rest and of 

 activity, are questions regarding which there is still far too much uncertainty to 

 admit of any definite statement being made. Until recently, the view, advocated b}' 

 Liebig, was generally held that physical exertion involved a positive waste of muscular 

 tissue, and that, consequently, an increase of the " flesh-formers," as the albuminate 

 constituents of the food were described, was required in proportion to the amount of 

 mechanical labour which the body was called upon to undergo. As a result of this 



