194 SOME MINUTE ANIMAL PARASITES 



the disease centres from whence it has spread to 

 many parts of India, though fortunately it has not 

 become permanently established in these other places. 

 It has been found, too, that in great centres like 

 Madras, there are some Kala-azar houses that is, 

 houses where person after person living in them has 

 succumbed to the complaint. There are also cases 

 of Kala-azar families, whose members have contracted 

 the disease successively. 



In Indian Kala-azar there appears to be no limit 

 to the age of the person attacked. Young and old 

 alike suffer. The distribution, then, of the infected 

 persons presents some difficulties, but the method of 

 transmission has presented far greater ones. Investi- 

 gations showed that contact with other infected 

 persons did not explain the transference, nor was 

 Kala-azar an air-borne disease. The persons afflicted 

 were rarely aware of the time when they contracted 

 the complaint, nor of any circumstances attending it. 

 The disease " appeared suddenly." Having excluded 

 air, water, food, and contact, some blood-sucking 

 insect was apparently incriminated. India contains 

 numerous animals that are skin parasites. Various 

 bed-bugs, fleas, head and body lice, sucking and 

 stabbing flies and ticks are found. Which of these 

 was the culprit, and was there more than one carrier ? 

 Such were the problems facing the investigators. 



From a consideration of the disease, its onset and 

 its distribution, it was 'obvious that if one carrier 

 alone occurred, it must be common and also widely 

 distributed. In the second place, the parasite is 

 not particularly common in the peripheral blood, so 



