=527. Classification.=—In the preceding parts have been set forth the
fundamental principles underlying the conduct of agricultural analysis
and a résumé of the best practice of the art. The analyst, as a rule,
will seldom be required to undertake investigations which are unnoticed
in the preceding pages. Cases will arise, however, in which problems
are presented which can not be solved by the rules already elucidated.
In respect of the great classes of agricultural bodies, it will be
observed that dairy products have already received special mention.
In respect of foods and fodders in general, it is evident that they
are chiefly composed of moisture, ash, carbohydrates, oils and proteid
matters. The methods of identifying, separating and estimating these
constituents have been fully set forth. It is not necessary, therefore,
to study in this part the analytical processes which are applicable
to cereals, cattle foods and other food products, further than is
necessary to present in the most important cases a working résumé of
principles and methods. There remain, however, certain products of
importance which require some special modifications of treatment,
and it is to these that the present part will be chiefly devoted.
Among these are found tobacco, tea and coffee, fruits, fermented and
distilled drinks and certain animal products. It is evident that an
enumeration of all agricultural products, with a description of their
methods of examination, would be impracticable in the available space
and undesirable by reason of the repetition which would be required.
In each case the analyst, in possession of the methods described, will
be able to adapt the means at his disposal to the desired purpose to
better advantage than any rigid directions could possibly secure.
In respect of the analytical methods of determining the nutritive
value of foods, they may be divided into chemical and physiological.
The chemical methods embrace the thermal and artificial digestion
investigations, and the physiological include those which are carried
out with the help of the animal organisms. In the latter case the
digestive process is checked by the analysis of the foods before
ingestion and of the excreta of all kinds during and after digestion.
It is evident that a detailed description of this method should be
looked for in works devoted to physiological chemistry.