It is a positive pathological fact that under-nutrition (or defective nutrition) through lack of the necessary amount of proteids in the diet exposes one more to infection by bacilli. This is plainly to be seen every day, especially in regard to tuberculosis; and as the best preventive to this we strongly recommend plenty of nutrition, especially rare meat and milk. We have personal knowledge of several cases of tuberculosis arising from a purely vegetarian diet (see, also, Chapter III). The findings of Grawitz[274] indicate that an insufficient proteid diet predisposes also to anæmia. The importance of this fact is emphasized by Sajous who has shown (1903) that defective nutrition weakens the activity of the pituitary, thyroid and adrenals, the products or secretions of which take an active part in the destruction of bacteria and their toxins. Footnote 274: Grawitz: “Klinische Pathologie des Blutes.” third edition, 1906. In our chapter on the destruction of toxic products by the liver, we referred to evidence gained from actual experiments, that under-nutrition predisposes to infection. We have referred to Roger and Garnier, who have proved that the liver loses its antitoxic properties in cases of under-nutrition, and it is probable that the other antitoxic organs exhibit a similar condition. There are two primary conditions on which infection depends: 1. The invasion of the microbes. The greater their number and virulence the more easily will infection take place. 2. The diminution of our normal resistance against infection, which, as we have seen in the third chapter, can be caused by different factors, among which is under-nutrition. In any case we are surrounded by countless millions of microbes every day, which are only too anxiously awaiting a favorable moment to attack us; and should we be so foolish as to encourage their attacks by adopting fads in our nourishment? The greatest danger of a strictly vegetarian diet is for those persons whose parents suffered from chronic cachectic diseases, such as tuberculosis, chronic alcoholism, etc., in whose cases the perils of infection are much more menacing. Should such expose themselves still more by insufficient nourishment, such a course can be called by no other name than culpable negligence, leading to suicide. It is the object of this book to demonstrate the best way to reach a ripe old age and to avoid disease; it is, therefore, my duty to emphasize the dangers of a sole vegetarian diet, especially for weak people.