CHAPTER LIV 



THE HISTORICAL DEVELOPMENT OF BIOLOGY 



Vocabulary 



Spontaneous, without cause. 



Mortality, death rate. 



Enumerate, to make a list of, to number. 



Rabies or hydrophobia, the disease caused by mad dog bite. 



Virulence, disease producing ability. 



Like all other sciences, biology has developed from small be- 

 ginnings, by the labor, study, and sacrifice of many men over a 

 long period of years. Biology might be said to have started when 

 man first became intelligent enough to observe the plants and 

 animals with which he was surrounded, and utilize or avoid them 

 as he found best. 



HARD WON KNOWLEDGE 



Circulation. We gain our present knowledge so easily and 

 take it so much for granted that we can hardly realize the struggles 

 by which even our simplest facts were obtained. 



Every child knows that the blood circulates in the arteries, 

 but the ancients believed that they were air tubes and it was 

 only in 1603, after much opposition, that Harvey was able to 

 fully prove this fact of circulation. 



Spontaneous Generation. We assume, as a matter of course, 

 that any plant or animal springs from a parent like itself, but up 

 to 1668 it was believed that maggots came from decayed meat, 

 that frogs came from mud, and that living things were produced 

 from non-living matter. At that date Redi discovered flies' eggs 

 and larvae and proved that the maggots were produced by flies. 

 The presence of bacteria in decaying substances was not explained 



until 1850-70. 



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