life: its nature^ origin^ and maintenance SCHAFER. 523 



based upon experiment. The transformation has opened out an 

 inimitable vista of possibilities in the direction not only of cure, but, 

 more important still, of prevention. It has taken place within the 

 memory of most of us who are here present. And only last February 

 the world was mourning the death of one of the greatest of its bene- 

 factore — a former president of tliis association ' — who, by applying 

 this knowledge to the practice of surgery, was instrumental, even in 

 his own lifetime, in saving more lives than were destroyed in all the 

 bloody ware of the nhieteenth century! 



senescence AND DEATH. 



The question has been debated wliether, if all accidental modes of 

 destruction of the life of the cells could be eliminated, there would 

 remain a possibility of individual cell life, and even of aggregate cell 

 life, continuing indefinitely; in other words, Are the phenomena of 

 senescence and death a natural and necessary sequence to the exist- 

 ence of life ? To most of my audience it will appear that the subject 

 is not open to debate. But some physiologists (e. g., Metchnikoff) 

 hold that the condition of senescence is itself abnormal ; that old age 

 is a form of disease or is due to disease, and, theoretically at least, is 

 capable of bemg eliminated. We have already seen that individual 

 cell life, such as that of the white blood corpuscles and of the cells of 

 many tissues, can under suitable conditions be prolonged for days 

 or weeks or months after general death. Unicellular organisms kept 

 under suitable conditions of nutrition have been observed to carry on 

 their functions normally for prolonged periods and to show no degen- 

 eration such as would accompany senescence. They give rise by 

 division to others of the same kind, which also, under favorable 

 conditions, continue to live, to all appearance indefinitely. But 

 these mstances, although they indicate that in the simplest forms 

 of organization existence may be greatly extended without signs of 

 decay, do not furnish conclusive evidence of indefinite prolongation 

 of life. Most of the cells which constitute the body, after a period of 

 growth and activity, sometimes more, sometimes less prolonged, 

 eventually undergo atrophy and cease to perform satisfactorily the 

 functions wldch are allotted to them. And when we consider the 

 body as a whole, we find that in every case the life of the aggregate 

 consists of a definite cycle of changes which, after passing tlirough the 

 stages of growth and maturity, always leads to senescence, and 

 fuially terminates in death. The only exception is in the repro- 

 ductive cells, in which the processes of maturation and fertilization 

 result in rejuvenescence, so that instead of the usual downward 

 change toward senescence, the fertilized ovum obtains a new lease of 

 life, which is carried on Into the new-^formed organism. The latter 



1 Lord Tiister was president at Liverpool In 189G. 



