MAIN PATHWAYS AND TENDENCIES 117 



protozoa, it has long been recognized that in order to 

 understand the real nature of living organisms one 

 must first become acquainted with the phenomena of 

 the Protozoa. The study of this single group has 

 assumed so much prominence that, already there has 

 been established in several universities a professor- 

 ship of Protozoology. 



The study of the lif e history of pathogenic protozoa, 

 of parasitic worms and of other disease-producing 

 and disease-carrying animal organisms has devel- 

 oped into a department of Parasitology. 



The application of zoological facts to the benefit of 

 mankind is a considerable feature of present-day 

 work. This is a continuation and extension of the 

 work inaugurated by Pasteur. Under this general 

 head are included the demonstration of the connec- 

 tion between insects and the propagation of yellow 

 fever, malaria, sleeping-sickness, typhoid fever and 

 other disorders. Although still in their infancy 

 much benefit has already accrued from zoological 

 studies of this character. 



Economic Entomology. Investigations in economic 

 entomology have become very active. They have 

 been stimulated by the economic need of the control 

 of the ravages by insect pests that have attacked 



