254 DEATH AND THE DURATION OF LIFE 



teristic old-age thickening of the walls of the blood-vessels 

 does not occur the attendant disorders are absent and life 

 is likely to be prolonged. But here again no satisfactory 

 reason is given for the so-called hardening of the arteries. 

 According to other students death is due to changes in 

 the nervous system, or in the rate of metabolism, or in 

 the relation of the nucleus to the cell protoplasm, or to 

 the modification of the physical or chemical constitution 

 of the cell ; and once more details are lacking. 



Still other investigators have suggested that the body, 

 as a result of its activities, generates poisons other than 

 those eliminated by the skin and kidneys, and these 

 accumulating in the cells prevent their operation. 

 Metchnikoff aroused great popular interest in this subject 

 by the suggestion that in man the large intestine harbors 

 great numbers of bacteria whose excretory poisons, ab- 

 sorbed by the body, produce disturbances ultimately re- 

 sulting in death. But attempts to destroy the bacteria 

 have not been productive of marked results so far as 

 the lengthening of life is concerned. 



It appears to be true that very often, if not invariably, 

 some one organ ceases to function and hence throws the 

 others out of adjustment. Beyond this point no scientist 

 has given a very satisfactory explanation of the immedi- 

 ate causes of death. 



Immortality of the Unicellular Organisms. — It is 

 a startling fact that death is not a characteristic of the 

 lowest forms of life. An amoeba or paramoecium, for 

 example, multiplies by the division of the cell into equal 

 halves. Parent A in the process becomes offspring B and 

 C. There is no death ; no corpse. These simple organisms 

 are thus potentially immortal. Some individuals, to be 

 sure, may be boiled, crushed, starved, or carried into un- 

 favorable situations where they perish; but these are 

 cases of accidental death only, and under no circum- 

 stances do such cells produce descendants. In other 

 words, every one of these primitive creatures is the de- 



