686 THE PHYSIOLOGY OF REPRODUCTION 



The term " Death " is employed in two separate senses ; it 

 may mean the death of the whole body, i.e. somatic death 

 (this being the sense in which it is ordinarily used), or it may 

 be applied to the death of the individual tissues, some of which 

 remain alive for many hours after the body as a whole is said to 

 be dead. The death of the body as a whole usually occurs 

 suddenly. As Michael Foster says : — " Were the animal frame 

 not the comphcated machine we have seen it to be, death might 

 come as a simple and gradual dissolution, the ' sans everything ' 

 being the last stage of the successive loss of fundamental powers. 

 As it is, however, death is always more or less violent ; the 

 machine comes to an end by reason of the disorder caused by 

 the breaking down of one of its parts. Life ceases not because 

 the molecular powers of the whole body slacken and are lost, 

 but because a weakness in one or other part of the machinery 

 throws its whole working out of gear." ^ 



The synchronous disturbance of two or more of the bodily 

 functions, such as is wont to occur in old age, may destroy that 

 co-ordination of the various vital activities, without which life 

 cannot continue. The stoppage of the heart's beat is the 

 ordinary criterion of death, and this is a true conception, because 

 the cessation of the heart's movements implies the arrest of the 

 circulation of the blood and the consequent starvation of the 

 tissues of the body. 



The tissues do not die simultaneously, for as already described, 

 some cells of the body are in process of disintegration through 

 the whole of life. After somatic death, the cells which make 

 up the nervous system usually die very rapidly. The same is 

 true of the gland cells ; but the muscles may remain sensitive 

 to external influences for many hours. In animals it has been 

 shown that the heart itself after removal from the body, if 

 kept under suitable conditions and perfused with an artificial 

 fluid resembling blood serum, may continue to live and undergo 

 rhythmical contractions for a considerable time. In the process 

 of death-stiffening, or rigor mortis, the muscles once more con- 

 tract spontaneously, and not till this has happened is their life 

 utterly extinguished. Rigor mortis is brought about by the 

 coagulation of the muscle plasma within the cells. It begins 



1 Foster, Textbook cf Physiology, Part IV., 5th Edition, London, 1891. 



