458 REPRODUCTION AND DEVELOPMENT 



and usually a precise one. Life is mostly dependent on metabolism, and 

 this in turn immediately on a supply of nutriment and of heat, and on 

 a prompt removal of katabolic waste. The instant the circulation all 

 over the body stops metabolism with certain exceptions comes at once 

 to a standstill. The brain is especially dependent from second to second 

 on a rapid stream of normal blood. Suppose a person in the standing 

 position to be shot with a large bullet through the heart, or that the 

 heart of a nlan with myocarditis bursts or stops short in extreme diastole. 

 In any of these cases the skeletal muscles instantly lose their tone because 

 the vast multitude of impulses which pass continually from the motor 

 centers to these sustaining muscles immediately cease. As a result the 

 man drops almost instantly when the blood-stream has ceased, and that 

 is immediately. In parts of the body other than the nerve-centers the 

 effective metabolism continues somewhat longer, and yet not long enough 

 to sustain the body-heat for any appreciable time, for the body cools 

 much as would one artificially heated when the source of heat is removed. 

 Recent work on the heart has shown that in cases where the organ is 

 not materially injured (as from lightning-stroke or from blows over 

 the solar plexus) it may be often started beating again by cardiac 

 massage either directly or through the pericardium. This indicates that 

 the nervous inhibitory shock has no permanent influence over the heart's 

 rhythmic pulsations. (See Expt. 15 in the Appendix). 



Respiration is another function whose cessation promptly kills, but 

 it does not do so as quickly as the stasis of the circulation, for survival 

 sometimes occurs after the intake of air has been stopped for as long as 

 five minutes. The modes of death other than nervous shock, the stopping 

 of the pulse, and the cessation of breathing we need not consider. It is 

 already obvious how individual death differs from cellular death. The 

 former term means the end of the general faculties movement, sensa- 

 tion, posture, etc. of the whole organism so far as appears from without. 

 The latter expression means the really essential physiological death. 

 Individual " death" may sometimes be recovered from; cell-death, so 

 far as we know, never. 



Physiology has at present no concern with the chief personal problem 

 of the human race persistence after death. This subject even psy- 

 chology still almost ignores, and scientific ethics knows next to nothing 

 of it. Death, indeed still "the Arch Fear in a visible form" to many 

 unthinking men, must from considerations other than these receive its 

 quietus in the soul of humanity. 



