The Prolongation of Life - Elie Metchnikoff

The author of this interesting book is a many sided man, a philosopher as well as a scientist, and a writer who charms by the simplicity of his style and the directness of his argument, holding the attention of his reader from the first page to the last. He makes his points with no show of polemics and meets his opponents with a gentle reasonableness which disarms the most captious critic of his theories. To the readers of his earlier work, "The Nature of Man," of which this is a continuation or a supplement, no commendation of the present essay is needed. They will find in it the same optimistic view of man's present and future, and the same fixed determination to dwell on the bright side of man's physical and mental constitution, without glossing over its imperfections, which characterized the preceding volume.
The author believes that most of us do not reach the length of life to which we are entitled, and if a few of us do so it is only through travail and by paying toll to a senility that comes before its time. Death from old age-natural death-is at present one of the rarest of phenomena but it is not impossible of achievement even now, and eventually it will be the normal end of man. Accidents from without it may never be possible to prevent absolutely, but the accidents of disease will in the course of time be excluded, and then man will live out his natural term happily and peacefully, and when the inevitable end arrives it will be welcomed; life having reached its physiological limit, the instinct of its preservation will be replaced by an instinct of death, and the final act will be accepted with the same peaceful content that one feels in dropping off to sleep after a day of pleasurable activity.
The cause of old age, that is to say, of premature and morbid old age, such as senility usually is, is, according to Metchnikoff, autointoxication, which either weakens the noble cells directly or acts upon them as a sort of opsonin, making them attractive to the phagocytes which destroy them and replace them by fibrous tissue. The elaboration of these auto-toxic agents takes place through bacterial action in the intestine, and chiefly in the large intestine. The colon is to the author of this book the bite noir of human anatomy, serving no useful purpose, and acting only as an immense culture tube for the noxious bacilli. Since the removal of this part is impracticable as yet, the best we can do in our efforts to attain to a healthy old age is to repress the growth of the intestinal bacteria by restricting the intake of meat and sowing the nutritive tract with the friendly lactic acid bacilli. This is done by taking either a pure culture of these bacilli or milk soured by their action.
This, in brief, is the argument of the treatise so far as relates to the subject noted by the main title, but there is much more, and this is the most interesting part, expressed by the subtitle, "Optimistic Studies," which treats of the ascent of man and of the relation of the individual to the species and to society. The limits of this review will not permit a further analysis of the work, which at best would be unfair to the author and unsatisfactory to the reader. It is a book which must be read to be appreciated, and its perusal will well repay anyone interested in the varied topics of human interest of which it treats.
-Medical Record, Volume 73 [1908]