Development of Hepatomonas of Kala-Azar, etc. 285 



test-tubes containing a few drops of 2 to 5 per cent, citrate of soda in 

 normal salt solution, in order to prevent clotting. Under these conditions 

 not only did the parasites remain alive for many days, but they also 

 multiplied very rapidly, became much enlarged, and after about three days 

 some of them developed into elongated flagellated bodies, which I took to 

 be a stage in the development of a trypanosome, although no undulating 

 membrane was yet present. This discovery was announced in the ' Lancet ' 

 of July 23rd, 1904, a few uncoloured illustrations were published in 

 September, (7) and a fuller paper tracing the stages of the development day 

 by day, with a coloured plate, in November (8) of the same year. Confirma- 

 tion of my discovery was first furnished by my assistant, Dr. G. C. 

 Chatterjee, (9) working in my own laboratory, and next independently 

 by Lieutenant Christophers, (10) working in Madras. Thirdly, Captain 

 Statham (11) and Lieutenant-Colonel Leishman also obtained the development, 

 and published their account of it, March, 1905. 



During the past year I have made a large number of experiments on the 

 conditions affecting the development of the parasites outside the human body, 

 with a view to obtaining a clue to the natural mode of infection, and early 

 in the present year I published a summary of the results obtained. The 

 most important conclusions arrived at were, that sterility is essential 

 to the continued development, and that flagellation takes place much more 

 uniformly and regularly if the citrated spleen blood is faintly acidified with 

 citric acid : facts which strongly point to the stomach of some blood sucking- 

 insect as the natural place of development of the parasite outside the body, 

 and I gave some clinical reasons for considering the common bed bug to be 

 the most likely conveyer of the disease. So much more abundant develop- 

 ment of flagellated stages has recently been obtained by the use of acidified 

 blood medium, that I have been able to make a more satisfactory study of 

 the exact mode of development, and to come to a definite conclusion 

 regarding the ultimate stage it reaches, and therefore propose to describe and 

 illustrate these later stages more fully than in my previous papers, and to 

 briefly discuss the bearing of the conditions affecting the development of the 

 flagellated stage of the parasite on the probable mode of infection of the 

 disease. 



Stages of Development of the Parasites observed in Acidified Citrated, Blood. 



In the first place, the development in acidified blood is much more 

 uniform than that obtained by the previous method, so that instead of 

 finding all stages present after three or four days, with a great preponderance 



x 2 



