Two years afterward Pineles, in an article published in the _Wiener klin. Wochenschrift_, comparing the origin of diabetes, tetany, and old age, came to the conclusion that old age was caused by the same agency (i.e., alteration of the ductless glands) as the other conditions mentioned. Sir Herman Weber, in his interesting work on the prolongation of life, also attaches great importance to degeneration of the ductless glands as a cause of old age. In his work on the same subject, Professor Metschnikoff admits, only partially, the truth of our theory on the causation of old age. He admits the great importance of the ductless glands in the pathology of old age, as they serve to destroy poisons. He denies, however, the relation of old age to a myxœdematous condition; but everyone who knows the pathology of myxœdema will see that the arguments of Professor Metschnikoff cannot stand, for they have no foundation. His arguments are that there is an œdema in myxœdema, but not necessarily in old age; that the hair falls out in myxœdema, and that myxœdematous women have abundant menstruation, while old women have none; that myxœdematous persons have strongly developed muscles, and old people, on the contrary, weak and feeble muscles. The truth is that there is often no œdema at all in myxœdema; that the hair often does not fall out in myxoedema, especially in its partial form (hypothyroidia); that myxœdematous women have, as a rule, no menstruation (atrophy of the ovaries); and that myxœdematous people have not a strongly developed muscular system, which is rather degenerated by a new growth of fat, or connective tissue, or a mucinous tissue, following the degeneration of the thyroid just as it follows its extirpation. Professor Metschnikoff also states that certain animals that soon become old do not develop cachexia after extirpation of the thyroid. This was the belief about eighteen years ago, but now we know that they all develop cachexia if the operation is so performed that the parathyroids, or at least some of them, are allowed to remain untouched. Professor Metschnikoff’s views have been greatly weakened by the far more extensive researches of Professor Sajous which have conclusively shown that the life process, its activity and duration, is dependent upon the ductless glands, including the thyroid. It is evident from the above considerations that all hygienic errors, be they errors of diet or any kind of excess, will bring about their own punishment; and that premature old age, or a shortened life, will be the result. In fact, it is mainly our own fault if we become senile at sixty or seventy, and die before ninety or a hundred.