LATENCY OF AFRICAN COAST FFVER. 22/ 



(lo) That some of these aforementioned indefinable cases, 

 when kept in a small enclosure by themselves so that they could 

 be re-infected with nymphse that had fallen as larvae off their 

 own bodies, developed in due course an attack of African coast 

 fever (parvse in the erythrocytes). 



These features were very puzzling and irreconcilable with 

 the known facts about coast fever. For four years I have been 

 attempting to unravel the mystery. 



I received some aid from reading Dr. Gonder's researches, 

 but his conclusions do not explain mv own observations in the 

 field. 



To proceed, an examination of the incidents of the out- 

 breaks tabulated and aggregated into months gave me a some- 

 what startling correlation with the features before observed, and 

 when the dates were still further enquired into, it was found 

 that those outbreaks in Southern Rhodesia which fell into the 

 month of February should have been relegated to January, and 

 those made known in the months of September, October and" 

 November should with more propriety be placed "in the months 

 of April, ]\Iay and June, when first cases did actually occur, but 

 remained unreported till the later date. 



Readjusted, we find that no actual outbreaks are to be put 

 down to the months of February, September, October and No- 

 vember, and in only one year did any apparently happen in 

 August. 



Further, in the Temperature Camp system of dealing with 

 coast fever, it has not infrequently happened that little or no 

 advance was made in the elimination of the disease during the 

 months of Alarch, April, Alay and June, but that in the suc- 

 ceeding months our efforts have met with success, which achieve- 

 ment is, in my opinion, not solely due to the operations, for 

 reasons which will hereafter appear. 



I shall start with Koch's bodies. What are these? 



I submit that they are aggregations of sexual elements 

 whose tuassing together is brought about — 



( I ) For their protection against extinction. 



(2) The evolution of sex, i.e., the formation of micro- and 

 macro- gametocytes, and, later on, ookinetes. This explains the 

 variation in the appearances of the Koch's bodies. 



(3) In quest of a dormant period. 



In December and the earlier part of the year, January to 

 May, they commence to separate from the surrounding tissues, 

 and the ookinetes (or oocysts), borne within lymphocytes, are 

 carried away to the cutaneous circulation. This disintegration 

 is particularly active in the months of January and February, 

 and continues into May, when it practically ceases, or rather the 

 Koch's bodies have by this time been disrupted, and are seen 

 again no more for a few months. 



From the cutaneous circulation the attached larvae imbibe 

 the parasite-laden lymphocyte (containing the ookinete or oocyst). 



