Septembee 6, 1912] 



SCIENCE 



301 



dueed by simple invagination. Some of 

 the cell-aggregates settled down to a se- 

 dentary life, becoming plant-like in ap- 

 pearance and to some extent in habit. 

 Such organisms, complex in form but 

 simple in structure, are the sponges. 

 Their several parts are not, as in the higher 

 metazoa, closely interdependent: the de- 

 struction of any one part, however exten- 

 sive, does not either immediately or ulti- 

 mately involve death of the rest: all parts 

 function separately, although doubtless 

 mutually benefiting by their conjunction, 

 if only by slow diffusion of nutrient fluid 

 throughout the mass. There is already 

 some differentiation in these organisms, 

 but the absence of a nervous system pre- 

 vents any general coordination, and the 

 individual cells are largely independent of 

 one another. 



Our own life, like that of all the higher 

 animals, is an aggregate life; the life of 

 the whole is the life of the individual cells. 

 The life of some of these cells can be put 

 an end to, the rest may continue to live. 

 This is, in fact, happening every moment 

 of our lives. The cells which cover the 

 surface of our body, which form the scarf- 

 skin and the hairs and nails, are constantly 

 dying and the dead cells are rubbed off or 

 cut away, their place being taken by others 

 supplied from living layers beneath. But 

 the death of these cells does not affect the 

 vitality of the body as a whole. They serve 

 merely as a protection, or an ornamental 

 covering, but are otherwise not material to 

 our existence. On the other hand, if a few 

 cells, such as those nerve-cells under the 

 influence of which respiration is carried on, 

 are destroyed or injured, within a minute 

 or two the whole living machine comes to a 

 standstill, so that to the bystander the pa- 

 tient is dead; even the doctor will pro- 

 nounce life to be extinct. But this pro- 

 nouncement is correct only in a special 



sense. "What has happened is that, owing 

 to the cessation of respiration, the supply of 

 oxygen to the tissues is cut off. And since 

 the manifestations of life cease without this 

 supply, the animal or patient appears to be 

 dead. If, however, within a short period 

 we supply the needed oxygen to the tissues 

 requiring it, all the manifestations of life 

 reappear. 



It is only some cells which lose their vital- 

 ity at the moment of so-called "general 

 death." Many cells of the body retain 

 their individual life under suitable circum- 

 stances long after the rest of the body is 

 dead. Notable among these are muscle- 

 cells. Mc William showed that the muscle- 

 cells of the blood-vessels give indications of 

 life several days after an animal has been 

 killed. The muscle-cells of the heart in 

 mammals have been revived and caused to 

 beat regularly and strongly many hours 

 after apparent death. In man this result 

 has been obtained by Kuliabko as many 

 as eighteen hours after life had been pro- 

 nounced extinct : in animals after days had 

 elapsed. Waller has shown that indications 

 of life can be elicited from various tissues 

 many hours and even days after general 

 death. Sherrington observed the white 

 corpuscles of the blood to be active when 

 kept in a suitable nutrient fluid weeks after 

 removal from the blood-vessels. A French 

 histologist, Jolly, has found that the white 

 corpuscles of the frog, if kept in a cool 

 place and under suitable conditions, show 

 at the end of a year all the ordinary mani- 

 festations of life. Carrel and Burrows have 

 observed activity and growth to continue 

 for long periods in the isolated cells of a 

 number of tissues and organs kept under 

 observation in a suitable medium. Carrel 

 has succeeded in substituting entire organs 

 obtained after death from one animal for 

 those of another of the same species, and 

 has thereby opened up a field of surgical 



