vii THE STAGES OF LIFE AND DEATH 311 



is no exact boundary separating life from death, but there 

 are intermediate states between them. Schultz and Virchow 

 applied the terms necrobiotic and necrotic to the processes through 

 which the vital elements gradually pass from life to death, 

 according to whether the element which perishes is disintegrated 

 or preserves its form. 



In the single cells or elementary constituents of the tissues 

 we see in various forms the changes leading to death. The study 

 of these changes (atrophy, degeneration, etc.) pertains to the 

 pathological anatomist and we have already given a brief descrip- 

 tion thereof. From our physiological point of view we may 

 remark that although much research work has been done bearing 

 on this point, it is not possible to fix the exact moment of the 

 death of single tissues ; it is generally caused by delicate and 

 gradual changes of a morphological, molecular, and chemical order, 

 which for the most part elude direct analysis. Only in the case 

 of the contractile tissues does rigor mortis afford us a clear fixed 

 point with which the first moment of their death, or at all events 

 the last act of their life, can be made to coincide (M. Schiff). 



The different tissues from birth to the end of life are subject 

 to retrogressive changes varying both in degree and rapidity. 

 Owing to this fact we find in the cataplastic phase an ever-increasing 

 lack of functional harmony in the organism as a whole, which 

 when it reaches a certain degree of intensity becomes incompatible 

 with life and inevitably leads to death. The immediate cause of 

 death is always intrinsic to the organism as a whole, even when 

 brought about by some external agency, but is extrinsic to the 

 elements of a large number of the tissues, being caused by functional 

 failure of the tissues and organs most essential to life, which 

 have undergone more radical changes and upon which the life 

 of the other tissues depends. This explains why death does not 

 take place at the same time in all parts of the organism, but 

 spreads from the higher tissues, which exercise more important 

 and controlling functions, to the less important tissues the function? 

 of which are of a subordinate and executive character. The 

 length of the life of the cellular elements from which the higher 

 organisms arise varies considerably. There are some cells in the 

 tissues which disappear and are renewed, thus securing the 

 functional continuity of the various organs and systems. The 

 corpuscles of the blood are constantly perishing and being regener- 

 ated; the cells of the epithelium of both internal and external 

 surfaces are continually degenerating, atrophying, and becoming 

 detached, and as continually being replaced by younger ones. On 

 the other hand, there are cells which have but a limited power of 

 regeneration and corresponding to this a very much longer life. 



B. Morpurgo (1898) showed that in the case of the functional 

 growth of the voluntary muscles the increase in size is due to 



