WHERE KALA-AZAR IS FOUND 193 



quently, it was suggested that perhaps developmental 

 stages might be found in some insect that probably 

 spread the disease. Thenceforward, the quest of the 

 carrier and the development of the parasite have pro- 

 duced an enormous amount of research on the part of 

 various workers ; but, unfortunately, the final identity 

 of the carrier of the disease has not been established. 

 In fact, it seems probable that more than one insect 

 may be involved in the transference of this dread 

 disease in different parts of the world. 



The quest of the carrier involved a study both of 

 the distribution of the disease and also of the biting 

 insects that were most common in the infected 

 districts. Kala-azar may be permanently located in 

 a place, when it is said to be endemic ; or it may 

 merely be temporary, having been introduced by the 

 advent of sick persons from an endemic area. The 

 original home of the malady seems to have been 

 Assam, and numerous places along the valley of the 

 Brahmaputra are infected. When the spread of 

 Kala-azar along the Brahmaputra valley, and especi- 

 ally in Assam, was investigated by Rogers, it was 

 found that the epidemic was checked by a narrow 

 region between the river and the Mikir Hills, and 

 had not spread farther north. Unfortunately, it has 

 now spread westward through Bengal, this time 

 following the valley of the Ganges. On the south 

 of the Ganges the Orissa country is infected, while 

 the south-east coast also is an area where the disease 

 is located, Madras being its chief stronghold. The 

 valleys of the Ganges and Brahmaputra and the 

 small but virulent centre at Madras represent roughly 

 13 



