METHODS OF RESEARCH 299 



that artificial cultivation of these organisms is 

 difficult. 



The work of these scientific investigators, the 

 bacteriologist and the protozoologist, is the founda- 

 tion on which the whole superstructure relating to 

 the recognition, treatment, control and eradication 

 of infective diseases rests. The work must be as 

 trustworthy as the present methods permit and the 

 conclusions based on it reached by sound reasoning, 

 or the practical measures founded on scientific 

 investigations will fail and the efforts of the 

 sanitarians be discredited. 



The ' specific' treatment of infectious diseases is 

 dealt with in a special article, and here it will suffice 

 to mention that several of these diseases are treated 

 by means of special 'sera,' resulting from the 

 researches of bacteriologists, and some by drugs, 

 acting ' specifically' upon the parasites within the 

 living body, drugs which have been investigated 

 and in some cases prepared by purely scientific 

 methods. 



The relationships of the fly to the parasite and 

 to the patient are problems which require for their 

 elucidation the joint researches of investigators 

 acquainted with the normal structures and functions 

 of the external and internal organs of flies, medical 

 men who treat the patients, and bacteriologists 

 and protozoologists, who investigate the parasites. 

 These investigators ascertain the conditions under 

 which the patients or their excreta can infect flies, 



