several severe illnesses which had damaged his heart, he lived longer than any of his family and passed the 70th milestone. His views on the method of production of senility aroused great interest and criticism not only from Marinesco,[122] Léri,[123] Sand, Laignel-Lavestine, and Voisin, who disputed the reality of the macrophages devouring the cells of the central nervous system, and Ribbert[124] who denied the existence of such a physiological intoxication and ascribed old age and death to the inevitable physico-chemical changes incident to life, but also from Salimbeni and Gery,[125] working in the Pasteur Institute, who while supporting most of his contentions did not consider that they provided the whole explanation, _e.g._, the involution of the ovaries at a fixed age was not thus accounted for. The means Metchnikoff advised for the postponement of senility and death were on much broader lines than the popular conception summed up by “sour milk” might suggest, for he expounded the philosophy of orthobiosis or a correct method of living. That intestinal toxaemia due to stasis has a very important influence in producing disease cannot be doubted, and Sir Arbuthnot Lane[126] has brought this prominently to our notice; while clothing in modern language the old ideas of the _primae viae_ he recalls to our memory Abernethy’s[127] panacea for many ills of the flesh, namely a blue pill at night followed by a mixture of gentian and senna in the morning. Among his collaborators Mr. Ernest Clarke[128] has insisted on the premature ageing of persons with intestinal stasis. From the analogy of syphilis, alcoholism, and other intoxications, which may produce degenerative changes simulating those found in old age, the hypothesis of intestinal toxaemia gains a certain amount of support, and it may not be so easy to exclude the agency of intestinal toxaemia as in the case of syphilis and some intoxications. But intestinal toxaemia may, as far as can be judged, be absent in healthy old age, and conversely be present in early life without causing the phenomena of old age. Further objections have been raised:--why should intestinal toxins be harmless for 40 or 50 years and then exert such a serious influence? why should women who are more subject than men to constipation be more long-lived; and that in constipated persons the faeces, as shown by Schmidt and Strasburger, contain fewer living bacteria than in health.[129] As applied to normal old age and death this hypothesis is pathological and therefore has rather failed to interest those who are working at the biological aspect. Perhaps the most that can be safely concluded in balancing the pathological and biological arguments is that while Metchnikoff’s view may be partially true it does not account for all senile changes, and that normal old age or senescence cannot be regarded as the result of toxins absorbed from the alimentary canal. OLD AGE OF CELLS AND CARCINOMA