PREFACE 



IT is the belief of the writer that one of the most pressing needs 

 of the present time is the education of the people as a whole in 

 the subjects of vital importance with which this book deals, 

 and an increased interest in this field of scientific work. Scien- 

 tists are the leaders of the world, and should constantly endeavor 

 to keep a little ahead of the lay population who follow them. 

 It is, however, important that the leaders should not only 

 blaze the trail, but should make it sufficiently easy to find so 

 that the followers may not fall too far behind. In the intense 

 fascination of exploring the trail, and the eager impulse to press 

 on to newer and ever newer fields, the scientist is in danger of 

 forgetting the handicaps of his followers, and of leaving them 

 hopelessly in the rear. Popular ignorance of many important 

 facts of parasitology and preventive medicine, even facts which 

 have been common bases of operation for scientists for many 

 years, is deplorable. To a large extent, however, the scientists 

 themselves are to blame, for in their enthusiasm for discovery 

 they have forgotten to make it possible for the laity to reap the 

 benefits of their investigations. There is even a tendency to 

 belittle the efforts of those workers who devote their energies 

 toward assisting the general public to keep in touch with scientific 

 progress. A book or paper which collects the work of others, 

 models it into a connected whole, and makes readily available 

 what before was widely scattered and accessible only to a skilled 

 " library-prowler," is stigmatized by the term " mere com- 

 pilation." It is the firm belief of the writer that this is not 

 only unjust but unwise. No less mental and physical energy, 

 if not perhaps even more, is necessary for efficient " mere com- 

 pilation " than for the addition of new facts to scientific knowl- 

 edge, and the value to civilization, which must be the ultimate 

 criterion by which all scientific work is judged, must be equally 

 as great, if not greater. The value of connecting related facts 

 is twofold: it helps to keep the world in general somewhere 

 nearly abreast of the times, and it is a distinct aid to further 



