128 



SCIENCE 



[N. S. Vol. L. No. 1284 



are trying to study and that they be fully in- 

 formed about it, so that they may be able to 

 grasp possible solutions of their problem. 

 They will, therefore, seek first to answer the 

 following questions: 



1. What is the history of the disease and 

 how long has it been known? How serious 

 has it been? 



2. What is its distribution? 



3. Does it occur in pandemic, epidemic, en- 

 demic or sporadic form? 



4. In what seasons of the year is it most 

 prevalent. 



5. Is there any apparent relationship be- 

 tween its distribution and the physical, bio- 

 logical or climatic features of the countries 

 where it occurs? 



6. Does it affect any particular group, oc- 

 cupation, sex, race or nation of people, or any 

 particular species of animal? 



7. May any wild animal be considered as 

 a reservoir? 



8. Has immunity or difference of suscepti- 

 bility been recognized and under what circum- 

 stances ? 



9. What are the symptoms of the disease? 



10. What have autopsies shown? 



11. What treatment has been designated? 



12. What is known or suspected about its 

 causation and dissemination? 



13. What possible theories can be advanced 

 to account for its causation and dissemina- 

 tion? 



A little time spent in collecting those facts 

 may save much effort later. 



VI. WHAT INSECTS SHOULD BE INVESTIGATED? 



A thorough entomological study of this 

 question may prove a valuable short cut to 

 the investigation. Many insects will be elim- 

 inated by the entomologist before he has 

 finished his preliminary work. He will at- 

 tempt to answer the following and many other 

 questions and will probably have to answer 

 them to the satisfaction of all his fellow 

 workers. 



1. What insects coincide in distribution 

 with the general distribution of the disease? 



2. What insects occur in peculiar habitats 

 of the disease? 



3. What blood insects occur in the locality 

 imder investigation? 



4. What is the relative abimdance of these 

 insects ? 



5. Is there a coincidence between the season 

 of abundance of any of these and of the 

 disease ? 



6. What insects occur in the homes, nests 

 or haimts of infected hosts? 



7. What insects are found on infected hosts ? 



8. What insects occur in the working 

 quarters of the patients? 



9. What insects would be most apt to affect 

 the particular group of hosts most susceptible ? 



10. What insects breed in or frequent the 

 excreta of the hosts? 



11. What insects are foimd at the food of 

 the hosts? 



12. What insects are found at the sources 

 of the food of the hosts, such as the milk? 



VII. WHAT IS NECESSARY IN THE TRANSMISSION 

 EXPERIMENTS ? 



The investigations which have preceded will 

 have narrowed the question down to certain 

 species or groups of insects which need to be 

 critically studied. All of those insects which 

 come in contact with the blood of the patient, 

 or the food of the patient, or the feces of the 

 patient, must be given special attention. At 

 this i)oint the bacteriologist, protozoologist or 

 the helminthologist finds his special work 

 beginning. There will be many points which 

 must be worked out by cooi)eration of the 

 parasitologist and entomologist. 



Considering first the blood-sucking insects, 

 it is necessary, to determine : 



1. Can the particular insect take up the 

 organism with the blood? 



3. Does the organism pass into the in- 

 testinal canal or does it stop at some point 

 en route? 



3. To what extent is the organism digested 

 by the insect? 



4. In what organs of the insect can the 

 parasite be demonstrated from day to day? 



5. Are any changes in the organism demon- 

 strable ? 



6. What path does the organism seem to 

 follow in the insect's body from day to day? 



