AGE AND NATURAL DEATH 69 



functions, and die. The same result may be brought about by 

 the local destruction of cells through disease, thus bacteria 

 may destroy the cells of the lungs in pulmonary tuberculosis, 

 a loss resulting in the weakening of other cells in the body and 

 finally in death through inability to obtain oxygen and give off 

 C0 2 . 



This gradual weakening of the cells and vital activities in 

 general led Weismann, a famous German biologist, to 'the con- 

 clusion that old age and natural death are penalties which the 

 higher organisms must pay for their privilege of differentiation 

 while the unicellular organisms, dependent only upon themselves 

 have an unlimited capacity of life, i.e., are potentially immortal. 

 These conclusions have been repeatedly challenged and numer- 

 ous experiments beginning with those of Maupas, 1888, have 

 been undertaken to show that protozoa like metazoa undergo 

 senescence and die from old age. Looked at from one point of 

 view it is obvious that all organisms contain cells endowed with 

 the potential of physical immortality, these, the germ cells, 

 hand down the race from generation to generation. Moreover, 

 it follows from the negation of spontaneous generation that all 

 living things are composed of protoplasm that has been living 

 continuously since life appeared on the earth. The experiments 

 of Maupas and of subsequent investigators have shown that 

 it is only in this sense that protozoa are physically immortal. 

 Maupas isolated Oxytricha, Stylonychia, and other unicellular 

 animals and kept the descendants isolated from other races 

 through 316, 319, etc., generations of simple division. Toward 

 the end of the time the cells became reduced in size and abnor- 

 mal in structure through loss of cilia and other organs, arid all 

 finally died under conditions similar to senile degeneration in 

 higher animals. Many other types of Infusoria, also, have 

 been watched through many hundreds of generations but the 

 physiological activities in every such experiment save one, 

 weaken and sooner or later, abnormal or deformed specimens 

 bring the race to an end. The one apparent exception is 

 the case of Paramecium aurelia which Woodruff has carried 

 on for seven years (over 4500 generations) without conjuga- 



