Nl'X'ROSIS AND DEATH. 263 



peared in old age. Cell repair is complete in early life, but gradu- 

 ally diminishes as the animal becomes aged. The activity of cells 

 and their life cycle is limited as is that of all active structures 

 either animate (ir inanimate. Therefore, if new cells are not pro- 

 duced and the old cells are not repaired their energy or vital 

 forces are finally exhausted and they degenerate and die. If large 

 numbers of cells of all tissues die the animal involved is incapaci- 

 tated and ultimately sufficient cells die to diminish the function of 

 the vital organs to such an extent that there is collapse and som- 

 atic death. 



I'hvsiologic death is initiated 1)y a gradual decline which 

 may continue until the individual dies. Or after a long per- 

 iod of slow decline, death may be sudden as a result of a sudden- 

 ly diminished function of a vital organ. Physiologic death is sim- 

 ilar in a way to the collapse of the one horse chaise which, as the 

 story runs, was used until it literallv fell to pieces. \'ery few 

 domestic animals die a physiologic death. Those animals whose 

 flesh is used for food are butchered long before physiologic death 

 would intervene, and those animals used as beasts of burden are 

 usually destroyed when their earning capacity is monetarily less 

 than the food they consume. 



Pathologic Death. 



Pathologic death signifies the ending of life prior to the time 

 that the vital forces have been exhausted. 



Etiology. — Pathologic death is that type caused In- accident 

 or disease process. Death primarilv is the result of permanent 

 suspension of heart action, respiration or brain functioning. 



Suspended heart action may be caused by influences acting upon 

 the cardiac nerve centers in the medulla or upon the heart mus- 

 culature direct. The significance of suspended heart action is 

 self evident. There being no blood circulating the tissue would 

 soon consume all available nutriment and then succumb. Tem- 

 porary arrest of heart action is called syncope. 



Respiratory arrest is usually the result of nervous influences 

 though clonic spams of the respiratory muscles would produce 

 a similar efifect. The absence of respiration implies the absence 

 of oxygen to oxidize the blood and the tissues and the absence 

 of oxygen for a considerable length of time results in carbon- 

 dioxide poisoning and death. Apnoea is a condition in which 

 respiration is arrested. 



Permanent arrest of all brain functioning even for a brief period 

 results in cessation of all the principal functions and death. 



