530 Introduction to the Study of Science 



been fed on the blood of a malarial patient and had become 

 infective. After eighteen days both developed typical cases 

 of malarial fever of the double tertian or three-day character. 

 Microscopic examination of the blood revealed the presence 

 of the malarial parasites. As neither of the men had had 

 this disease previously, the result established the truth of the 

 theory. 



258. An example of scientific method. This is an excellent 

 example of the way in which scientific men deal with a difficulty 

 or a problem. It illustrates the spirit of those who do the 

 scientific work of the world, and may serve as a guide to every 

 one in striving to understand the difficulties and problems of 

 daily experience. Some of the chief steps involved in the whole 

 course of investigation may be stated briefly in order to em- 

 phasize the method of scientific procedure. 



1. The first aim is to locate exactly and form a clear idea of 

 the difficulty experienced. This means that facts must be com- 

 piled, and a definite statement made of the problem in order 

 to make clear what is known and what is unknown. 



2. This statement of the problem and its difficulties suggests 

 possible explanations or solutions. 



3. The explanations or solutions suggested are carefully 

 considered before applying experimental or practical tests in 

 order to avoid waste of time and energy. 



4. The promising explanations are tested in various ways. 

 Of a thousand ideas advanced it may often happen that only 

 one is worthy of thorough test. It was so with the problem of 

 malaria and its transmission. The idea selected for thorough 

 test was that malaria and possibly other diseases may be 

 transmitted by blood-sucking insects. It had to be proved by 

 the discovery of new facts and then tested by these facts. 



5. Practical tests may be necessary, as with malaria. When 

 it had been proved that the bite of the Anopheles mosquito, 

 which had become infective, inoculated healthy persons with 

 the malarial parasite, the case seemed to be closed. But it also 



