The examples here referred to are not commonly considered dis-ease, because we know the particular or immediate cause of the physical disturbance. Modern knowledge now shows us that the most prolific cause of what is commonly known as dis-ease is but the interference with cell activities, either by the deficiency or by the excess of nutritive substances, or by the presence of irritating and disturbing poisons. This condition may be caused by an unbalanced diet containing too much of certain nutritive elements, or too little of others, causing surfeiting on the one hand and starvation on the other. [Sidenote: Man still in the childhood state of development] [Sidenote: Hunger, thirst, and taste are Nature's language] Health is the normal condition, and in spite of Ingersoll's witticism, it is more "catching than dis-ease." Were it not so, the race would long since have become extinct. With reference to body-health, however, we are still in the childhood stage of development, and the science, therefore, of building man to his highest estate--of lifting his mental, moral, and physical faculties to their highest possible attainment, is worthy the labor of the greatest minds. That person, then, who enjoys the best health, the keenest mentality and power of perception, the highest physical and emotional organism, is he who can select such articles of food as will supply all the constituent parts of the body most nearly in the right or natural proportions. The science of feeding, upon which this mainly depends, becomes possible only when food is taken in accordance with certain fixed, natural laws. These laws are not complicated--they are simple and easy to comprehend. Nature is constantly endeavoring to aid us in their solution. Hunger, thirst, taste--all the instincts and natural desires of the body are merely Nature's language. To interpret this language, and to obey the laws it lays down is man's highest duty to himself and to his race. There are very few true dis-eases. Nearly all of the abnormal physical expressions given off by the body can be traced to a few primary causes, and most of these causes can be removed by ascertaining and removing other causes that precede them. [Sidenote: Classification of dis-ease, a matter of convenience] The classification of dis-eases is merely a matter of convenience, and is of no practical importance between the food scientist and the patient. It merely enables the one who has studied these classifications to convey his knowledge or information to the lay mind. The dis-eases which will most interest the student will be those caused by a lack of nutrition, or by a surfeit of nutrition; that is to say, a form of starvation caused by a lack of certain nutritive elements, and overingestion caused by an excess of certain other nutritive elements.