Any attempt to gain information in regard to the state of nutrition of an individual must concern itself with two strictly to be distinguished inquiries, viz.: the condition of the protoplasm, i. e., of the muscular tissues, and the condition of the reserve materials, especially of the adipose tissues.

1. Muscular Tissues

The mass of the muscles, the condition and bulk of which can easily be ascertained, furnishes a measure of the content of the body in protoplasm. In estimating the latter, however, the large glandular organs and, above all, aside from the muscles, the blood must also be considered. One can calculate that ordinarily the quantities of albumen in the musculature and in the blood run approximately parallel. An exception to this rule is found in certain diseases, as special diseases of the blood-forming organs, neuropathic and myopathic atrophies, etc. An individual with a scanty musculature is always also suffering from atrophy of the blood; here an examination of the blood need not necessarily reveal any deviations from the normal in its composition, but the mass of the blood is reduced. Some authors designate this condition of the blood as oligaemia vera, others probably more correctly, as an atrophy of the total blood. In absolute fasting and in chronic undernutrition valuable proofs for this contention are found, the mass of the blood decreasing proportionately to the loss of muscle tissue, whereas pathological changes in the composition of the blood do not appear until later. In chronic pulmonary tuberculosis one also sometimes witness a similar sequence of events, viz.: high degrees of emaciation, great pallor of the skin and of the mucous membranes, but nevertheless almost normal blood findings. Whenever the blood suffers more than the musculature then special factors that inhibit blood formation or that accelerate blood destruction must be operative. In all such cases the blood composition will always be found abnormal (oligocythemia, low percentage of hemoglobin, thinning of plasma, etc.).

No optimum can be formulated for muscular de velopment or for muscle bulk. We should be content to attain the greatest development of which each individual is capable. Definite limits are set to the development of the musculature by individual peculiarities and often hereditary factors, that consequently may be called endogenous. Not every individual can be developed into an athlete even though every effort may be made in this direction from childhood up. Here and there special conditions may obtain that render it inadvisable to aspire to the highest individually possible muscular development, as, for instance, cardiac disorders, certain forms of paralysis, deformities, etc. As a rule, however, that degree of muscular development that can be obtained without detriment to the organism in general or to special organs should be striven for. Essentially the same considerations are valid in the case of the blood; true, one is here always haunted by the fear of "plethora"; and, as a matter of fact, there seem to be conditions in which - aside from hydraemia - the mass of the blood becomes increased beyond a point that is of value to the organism and that exceeds the average degree to which the bloodvessels should be filled. Why this condition, that has been designated as "hypertrophy of the blood," in contradistinction to the "atrophy of the blood," mentioned above, should be particularly common in chronic respiratory and circulatory disorders, often associated with obesity, we do not know. Modern investigation has adopted an attitude of negation towards the old, clinically by no means unimpor tant conception of "plethora," that is hardly justified. Finally there remain to be mentioned certain rare and etiologically also obscure cases of polyglobulemia (erythrocytosis).

Aside from these exceptions the axiom can be maintained that the two main albumen carriers of the body, the muscles and the blood, develop, increase and decrease in a parallel manner.

2. Adipose Tissues

Whereas in the case of muscular tissue one cannot very well formulate an optimum of nutrition, one can readily do so in the case of the adipose tissue of the body. Here one is justified in speaking of a "medium condition of nutrition" and in declaring this to be the optimum. This optimum, however, has fairly wide boundaries. Expressed numerically it presupposes a fat content of from 18 to 22% of the body weight in an adult man, of from 25 to 28% in an adult woman. The layman who judges exclusively from external appearances will never hesitate to designate an individual as thin, normally developed, or fat. As a matter of fact, however, the situation is very complicated. In the first place it is always important to determine the relation between the musculature and the adipose tissue and to include it in the calculation. In order to do this properly one must have medical training and education, and there are other questions besides that a physician alone can decide. He knows, for instance, that under certain pathological conditions an adipose development that exceeds the average is desirable as, for instance, in tuberculosis and diabetic subjects. He knows that in numerous neurasthenics, even if their muscular development is very great, all attempts at a cure become abortive unless one succeeds in increasing their reserve material; this applies particularly to sufferers from gastric and intestinal neurasthenia. This peculiar phenomenon is difficult to understand, but it is constantly being corroborated by practical experience. In other morbid conditions on the other hand it may appear desirable to reduce the fat of the body to a point that lies below the "medium state of nutrition." To this category belong numerous disorders of the respiratory and circulatory apparatus, as well as certain neurogenous, myogenous and arthrogenous disorders of the organs of locomotion, particularly about the lower extremities.

It will be seen, therefore, that the question whether or not an individual is in the optimum of development as far as his adipose tissues are concerned can only be solved if, aside from external appearances, the relation between the musculature and the adipose tissue, as well as a series of individual factors, are all considered. In most cases the matter is quite clear and very apparent. In others again it may become necessary to carefully weigh all the circumstances of the case before active modification of existing conditions is undertaken by the physician.