TRANSMISSION OF TROPICAL DISEASES. 11 



clinically from this exists in the Mediterranean littoral, but 

 there is this difference, that in these countries the disease 

 is almost entirely confined to children, though very occasionally 

 adults also contract it. Both these diseases are caused by 

 parasites which are about the size of one-third of a red cell 

 and have two nuclei. They can be cultivated on blood media, 

 where they change into slender spindle-shaped flagellates. 



Further, in the Mediterranean countries there is a wasting- 

 disease in dogs which is also due to a parasite indistinguishable 

 from that producing the disease in children and adults in 

 India, and it is thought that there is some connection between 

 the disease in dogs and the disease in children. 



The existing evidence is to the effect that this disease 

 in children is transmitted from dogs by the agency of fleas, 

 though others disbelieve this and claim that mosquitoes are 

 the transmitting agents. There is no evidence however 

 that in India this disease in dogs exists at all, so that we are 

 puzzled by the apparent relationship of the dog disease in 

 the Mediterranean and the non-relationship in India. 



The matter is further complicated by the fact that in 

 many parts of the world a disease occurs, viz., Oriental sore. 

 This is purely local skin affection, but in the sore, parasites 

 are found indistinguishable from those that occur in the 

 general infection of kala-azar. 



I should mention in connection with these diseases some 

 interesting French work recently done. It is known that 

 in the gut of many insects spindle-shaped flagellates occur. 

 Laveran and Franchini find that the injection of these 

 flagellates into mice gives rise to non-flagellate forms in the 

 organs indistinguishable from kala-azar parasites, and in 

 fact the mice die of the infection. Now in these diseases, 

 viz., kala-azar, infantile kala-azar, dog kala-azar, and tropical 

 sore, numerous investigators have been searching actively 

 for the transmitting agent, e.g., fleas, bugs, mosquitoes, 



