314 PHYSIOLOGY CHAP. 



to indicate accurately the internal condition determining death, the 

 problem must be stated very differently : granted that each of the 

 three centres of life mentioned by Bichat is indispensable to 

 the life of the whole organism we must ask : Which of them has 

 the least power of resistance, i.e. which is the primum moriens ? 



The reply to this question may be based upon the study of 

 the more or less prolonged survival of the various organs when 

 severed from the body of the animal, a subject which we have 

 already had occasion to describe and discuss in different chapters 

 of this treatise. We know that the kidneys, intestines, liver, and 

 smooth and striated muscles are capable of surviving for a con- 

 siderable time when separated from the animal, especially if 

 subjected to artificial circulation. With respect to the heart, it 

 will suffice to call to mind the surprising results of the experiments 

 of Kuliabko and the younger Hering, who succeeded in reviving 

 activity in the heart of both man and animals many hours or 

 even three or four days after death. With reference to the 

 nervous centres (which undoubtedly represent the dominant force 

 in the life of the higher organisms), we know, on the contrary, that 

 they offer less resistance than all the other tissues when the 

 external conditions necessary for life are changed, and more 

 especially when they are deprived of oxygen. The experiment 

 made by Pfliiger on the frog, to which we referred in Vol. I., 

 Chapter III., is really surprising in its simplicity considering the 

 importance of the results. These showed : (a) that the heart after 

 the frog had been absolutely deprived of oxygen for twenty hours 

 could still be revived by repeated insufflations of air ; (&) that 

 the muscles of the skeleton could be brought back to life after 

 two hours had elapsed ; (c) that still later the action of the spinal 

 reflexes could be renewed, that is, the vitality of the nerve cells of 

 the spinal cord could be restored ; (d} that still later spontaneous 

 respiration can be induced, that is, automatic activity of the cells 

 of the bulb; (e) that the voluntary movements, i.e. the function 

 of the cells of the higher centres of the brain, cannot be revived. 

 Hence the brain is the part of the nervous system which is least 

 capable of withstanding the deprivation of oxygen. This experi- 

 mental fact leads us to the conclusion that the primum moriens, 

 the internal condition causing death (whether as the result of old 

 age, disease, or external injuries) is invariably the brain, the 

 supreme ruler to which all the functions of the life of man and 

 the higher animals are directly or indirectly subject. 



The result of Kibbert's recent work, Der Tod aus Alters- 

 schwache (1908), absolutely bears out this conclusion. In support 

 of his thesis he adduces the arguments which may be inferred 

 from the organic decay noticed in the old, the frequent drowsiness, 

 the gradual weakening of the senses, in fact the whole range of 

 phenomena of the senile mind which we have just described ; 



