Persons suffering from the milder form of this disease often present a rosy and healthy appearance, and as we have pointed out previously, often look younger than their age. We believe that, as we shall show further on, this fact is not without relation to the condition of the thyroid in this disease. We have shown by researches made in the laboratory of Professor Minkowski, then of the Augusta Hospital in Cologne, that in diabetes the thyroid contains large, sometimes enormous, quantities of colloid substance, thus indicating a condition of thyroid hyperactivity. As we have mentioned in the first chapter, corpulence is often one of the first symptoms of old age, and we have also insisted upon the fact that this can be brought about by infectious diseases (e.g., typhoid, pneumonia, scarlet fever, etc.). As we have also mentioned the fact, in the first chapter, that old age can be brought about by an infectious disease which acts upon the ductless glands, especially the thyroid, we believe it will be necessary to enter a little more in detail into this subject, to which we will devote the next chapter. We will enlarge upon the fact that our immunity against infectious diseases is entirely dependent on the proper working order of certain ductless glands. ------------------------------------------------------------------------ CHAPTER III. ON THE AGENCIES WHICH GOVERN IMMUNITY AGAINST INFECTIONS AND INTOXICATIONS—THE ORIGIN OF FEVER. FROM the moment of our birth we are constantly exposed to the incessant attacks of innumerable bacteria and to the effects of a large amount of poisonous material formed within our body or introduced from without, and if we survive this ceaseless battle it is due to the powerful weapon we possess in the internal secretion of the ductless glands, especially of the thyroid gland. That this gland possesses very energetic antitoxic properties can be shown by the fact that when it is extirpated animals or persons very readily acquire infectious diseases of all sorts. Thus, the late Professor Charrin,[44] of Paris, showed several years ago how readily dogs that have lost their thyroid succumb to all possible infections. Professor W. S. Greenfield,[45] of Edinburgh, has found that persons suffering from myxœdema (athyroidia) very often die from tuberculosis, and Professor Pel,[46] of Amsterdam, found a great frequency of tuberculosis in the families of myxœdematous persons. This coincides with the conclusions of Prof. G. R. Murray,[47] Professor Lanz, and ourself, that the properties of the thyroid can be inherited. Sajous has shown, moreover, that the pituitary, the adrenals and the thyroid constituted the autoprotective mechanism of the body against disease, a fact not only sustained by the above evidence, but also by a vast number of additional facts. Footnote 44: Charrin: “Les Defenses naturelles de l’organisme,” Paris, 1898 (Masson). Footnote 45: