Leiskmanioses and Insects 221 



Brumpt objects that they and other workers who thought to trace 

 the development of Leishmania infantum were apparently misled by 

 the presence of a harmless Herpetomonas which infests dog fleas in all 

 countries, even where the leishmaniasis is unknown. 



Basile (1910 and 191 1) however, carried on numerous experiments 

 indicating that the disease was transferred from children to dogs 

 and from dog to dog by the dog flea, and was able to find in the 

 tissues of the insects forms perfectly identical with those found in 

 children and in dogs suffering from leishmaniasis. He also found 

 that Pulex irritans was capable of acting as the carrier. 



Of the cutaneous type of leishmaniasis, the best known is the so- 

 called "Oriental sore," an ulcerative disease of the skin which is 

 epidemic in many tropical and subtropical regions. The causative 

 organism is Leishmania tropica, which occurs in the diseased tissues 

 as bodies very similar to those found in the spleen in cases of 

 kala-azar. The disease is readily inoculable and there is no doubt 

 that it may be transferred from the open sores to abraded surfaces of 

 a healthy individual by house-flies. It is also believed by a number 

 of investigators that it may be transferred and directly inoculated 

 by various blood-sucking insects. 



Ticks and Diseases of Man and Animals 



We have seen that the way to the discoveries of the relations of 

 arthropods to disease was pointed out by the work of Leuckart and 

 Melnikoff on the life cycle of Dipylidium, and of Fedtschenko and 

 Manson on that of Filaria. They dealt with grosser forms, belonging 

 to well-recognized parasitic groups. 



This was long before the role of any insect as a carrier of patho- 

 genic micro-organisms had been established, and before the Protozoa 

 were generally regarded as of importance in the causation of disease. 

 The next important step was taken in 1889 when Smith and Kil- 

 boume conclusively showed that the so-called Texas fever of cattle, 

 in the United States, is due to an intracorpuscular blood parasite 

 transmitted exclusively by a tick. This discovery, antedating by 

 eight years the work on the relation of the mosquito to malaria, had a 

 very great influence on subsequent studies along these lines. 



While much of the recent work has dealt with the true insects, 

 or hexapods, it is now known that several of the most serious diseases 

 of animals, and at least two important diseases of man are tick 

 borne. These belong to the types known collectively as babesioses 

 (or " piroplasmoses") , and spirochetoses. 



