12 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



sandflies, etc., and vainly experimenting to procure develop- 

 mental cycles in these supposed transmitting agents on the 

 analogy of malaria, sleeping sickness, etc. In the case of 

 the dog disease successful transmission results have indeed, 

 it is stated, been got through the agency of fleas. If we 

 assume for the moment the accuracy of these transmission 

 experiments, it does not, it seems to me, follow — keeping 

 in view Laveran and Franchini's experiments — that they 

 necessarily prove that the flea is the transmitting agent in 

 the accepted sense, viz., that it transmits from dog to dog 

 in this case. It is possible that the dog disease is due to the 

 inoculation by fleas of their natural gut flagellates, and that 

 each case of the dog disease arises de novo from the flagellates 

 of a flea ; the disease is in fact a flea-dog disease, but not a 

 flea-dog-flea disease. We might, indeed, call it hemi-cyclical 

 transmission, not cyclical, and so for all the other similar 

 infections kala-azar, infantile kala-azar, and tropical sore. 

 But I need hardly remind you that this is sheer hypothesis. 

 Should it prove to be true it may also apply to diseases due 

 to helminths and possibly bacteria. For instance, we have 

 a Nematode disease in man and cattle characterized by the 

 presence of nodules of worms in the skin, but as no larvae 

 apparently exist in the blood it is at present difficult to 

 understand how the nematodes get out, i.e., the disease gets 

 transmitted. On the hypothesis I have just put forward, 

 the explanation would be that these nematodes were derived 

 from forms existing in the guts of insects or possibly in water. 

 I would suggest also that Sarcosporidia form an example of 

 hemi-cyclical infection, i.e., they get into animals but do 

 not get out. I must apologise for this digression into the 

 pleasant and easily-trod path of hypothesis, but will now 

 return to matters of fact. 



