A volume might be written in description of the unending list of patent and proprietary food preparations. Many, perhaps most all, of these are prepared with the sincere desire and earnest attempt to furnish a needed and valuable article. Many of the products have accomplished this to a greater or less degree. Some of the proprietary foods possess great value. Others possess a little value. Even an enumeration of these foods in the preparation of a brief manual may be properly omitted. A few general principles may be formulated as a sort of guide regarding such preparations in general.

I. Chemical Analysis Not Conclusive

A common fallacy which has deceived not only the producers and dealers, but also physicians and dietitians, is that a food whose chemical analysis shows that it contains proteins, fat, carbohydrates and salts in the proportions approximating those in which these foodstuffs exist in some common wholesome food should be equally nourishing and wholesome. It must be admitted that it does not infrequently occur that such a patent and proprietary preparation is well borne by an infant or an invalid as the case may be, and seems to, and perhaps does, supply the nutritional needs of the body. On the other hand, a large proportion of individuals find the flavor of the preparation unpleasing and find that if they eat it at all it is taken under protest and does not seem to agree with them. It will not fulfill the nutritional requirements of their bodies. Chemically, the food is all right. Physiologically, it is faulty and cannot be continued without marked disturbance of nutrition of the individual.

II. Predigestion Unnatural

A large number of the proprietary foods, patent foods, and widely advertised breakfast foods are partly predigested. Proteins having been reduced to proteoses and peptone, starches having been reduced to dextrins and sugars. Such predigested foods or portions of foods are naturally quickly dissolved and readily absorbed. The fact that they are predigested does not interfere with their action in the body once they are absorbed. The difficulty with predigested food must be sought in another direction. It does not stimulate the action of the digestive glands. The work of these glands having been already accomplished, they rest; their inactivities become habitual if the use of the predigested food is long continued. In this way a sluggishness of the digestive system may be gradually induced which will require weeks or even months to correct. Predigested food is as bad for digestive glands as presawed wood is to muscles. If a father saws the wood that his boy should saw, thus relieving the boy's muscles from vigorous activity, these muscles will become flabby and weak. Similarly, if a father gives his boy predigested food, the glands, relieved of the necessity of doing any work, become inactive and weak. The principle, therefore, that is involved is a far-reaching biological principle, whose application is as broad as are the manifestations of plant and animal life on the earth. Unused functions become sluggish and weakened; nonfunctioning tissues become flabby and atrophied.

Predigested food, as peptonated milk and starch reduced to sugar and dextrins, may properly be used temporarily to tide over a nutritional crisis. Their use, however, should be discontinued at the earliest possible moment.

III. Liquid And Pulpy Preparations

Liquid and pulpy preparations should make only a very small proportion of the diet of a healthy person after the second year, for a reason similar to that just cited above. These liquid and pulpy foods might be called prechewed foods. After an individual gets teeth he must use them if he would keep them. While liquid and pulpy foods may be introduced into a menu, they should not make up the whole menu, except in the case of infants and invalids. In an infant dietary solid foods should be introduced as soon as the child has developed an armament of teeth with which he can chew. In the case of the invalid solid foods should be used as soon as the temporary condition has passed, which necessitated their abandonment in favor of the liquid and semi-liquid foods.