GENERATION, SEX AND ONTOGENY 243 



the body parts begin, and soon the animalcule crawls about, 

 begins again its life where it had been interrupted. Various 

 other small animals, such as vinegar eels and certain Protozoa, 

 show similar powers. Certainly here is an interesting problem 

 in life and death. 



When death comes to one of the animals with which we 

 are familiar, we are accustomed to think of its coming to the 

 whole body at some exact moment of time. As we stand 

 beside a pet which has been fatally injured, we wait until 

 suddenly we say, " It is dead ! " As a matter of fact, it is diffi- 

 cult to say when death occurs. Long after the Heart ceases 

 to beat, other organs of the body are alive that is, are able to 

 perform their special functions. The muscles can contract for 

 minutes or hours (for a short time in warm-blooded, for a long 

 time in cold-blooded animals) after the animal ceases to breathe 

 and its heart to beat. Even longer live certain cells of the 

 body, especially the amceboid white blood corpuscles. These 

 cells, much like the Amoeba in character, live for days after the 

 animal is, as we say, dead. The cells which line the tracheal 

 tube leading to the lungs bear cilia or fine hairs which they 

 wave back and forth. They continue this movement for days 

 after the heart has ceased beating. Among cold-blooded ani- 

 mals, like snakes and turtles, complete cessation of life func- 

 tions comes very slowly, even after the body has been literally 

 cut to pieces. 



Thus it is essential in denning death to speak of a complete 

 and permanent cessation of the performance of the life processes. 



