ALGERIA 73 



DisTiiiBUTroN OF Anophelinks 



They in the first place sliow, as Christopliers, 

 Stephens, and Koch have shown in AVest Africa, in 

 the case of the black races, that in Algeria the 

 human carriers of the disease, or the reservoirs, are 

 the Arabs, who harbour tlie malarial parasites in their 

 blood without showing any pronounced symptoms of 

 malarial fever. From this fact they reason that the 

 danger of infection is in direct relationship to the 

 number of indigenous inhabitants. 



AA^itli regard to the distribution of the insect 

 carriers — the anophelines — they rightly insist that the 

 larvffi are not found in the lakes or in the rivers ; 

 that they are, in fact, strictly confined to the edges. 

 They also lay stress upon the fact that careful 

 cultivation of the land diminishes the breeding places, 

 giving as examples the amelioration of malaria which 

 has followed vine plantation, due entirely to the fact 

 that for the proper cultivation of the vine it is 

 essential that there be no stagnant water. In a sub- 

 sequent chapter it will be observed that the same im- 

 provement has occurred in connection with the tobacco 

 plantations in Sumatra, Avhere the most careful irriga- 

 tion is necessary to produce the best leaf. In this way 

 the carefully irrigated plantations contrast markedly 

 with the improperly drained areas around, and are free 

 from malaria. This clearance of malaria following on 

 careful irrigation is also seen to a considerable extent 

 in tea, cocoa and coffee plantations ; but the reverse 

 has also happened where the irrigation has been less 



