Metchnikoff’s Pathological Explanation
As an alternative to the belief that there is an inherent quantum of vitality which may be harmfully or beneficially influenced by environment and the wear and tear of life, it has been suggested that the process of ageing depends solely on external factors and that either there is no intrinsic limitation to the life of the organism or that the possibility is entirely cast into the shade by predominance of extrinsic influences. This doctrine is free from any tinge of fatalism and has the advantage that it is a direct stimulus to efforts in the direction of hygiene in all its forms; for as things are now old age owes its discomforts to superadded and in most instances avoidable complications. Élie Metchnikoff, as is well known, attributed the senile accompaniments of advanced years to pathological and preventible causes, namely toxaemia induced by alcohol, syphilis, and especially by bacterial activity in the colon which in common with Barclay-Smith and Arbuthnot Lane, he regarded as a harmful phylogenetic relic, this point of view being expressed by the epigram “the longer the colon the shorter is life.” He considered that the putrefactive bacteria in the colon produce phenol, indol, skatol, and aromatic bodies which cause degenerative changes in the cells of the body; and that the more resistant macrophages, which do not attack healthy tissues, absorb the damaged cells. He therefore employed means to prevent excessive bacterial activity in the large intestine, and in addition to care in diet so as to diminish the risk of introducing bacteria into the alimentary canal, he advocated the destruction of putrefactive bacteria in the colon by means of sour milk and cultures of Bacillus bulgaricus, which form lactic acid and thus render the contents of the bowel acid and unsuitable for the growth of the harmful micro-organisms. Metchnikoff thoroughly practised his doctrine, but he did not begin his regime until he was well over fifty, and, in spite of 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.