7 6 



which one would reasonably expect them to be least numerous. The 

 explanation with regard to the residences of Europeans has been 

 given. In the granitic or gneissic hills there are numerous natural fis- 

 sures, sometimes large numbers of artificial excavations that have 

 served as mortars for grinding corn. In these fissures and excava- 

 tions mosquitoes breed in large numbers. On the other hand, the 

 low-lying country almost always consists of porous sandy soil through 

 which rain is filtered into a subsoil of gravelly formation. A clay 

 surface along which rain water runs is exceptional. The final result 

 is that for six months in the year the propogation of mosquitoes is 

 practically at a complete standstill in the interior. The soil becomes 

 extremely dry, and remains in that condition for several months. One 

 hardly ever sees a pool anywhere save in the beds of rivers and creeks 

 of a considerable size. As these latter are full of small fish the mos- 

 quito larvae bred there have extremely little chance of survival. Dur- 

 ing the dry season there was not a mosquito to be seen at Oloke-Meji, 

 on the Ogun River, a place that one would have expected to be infested 

 with them. It is the sandy porous soil of this country and its long- 

 continued dry season that reduces the number of mosquitoes here to 

 a very small fraction of those met with in a place like British New 

 Guinea, for example. It would perhaps be possible to exterminate mos- 

 quitoes altogether in the Lagos hinterland if it were practicable to pre- 

 vent their production near the coast, and their arrival from elsewhere. It 

 is quite clear that the dry season here is a mighty factor against the 

 mosquito and a most encouraging ally of his enemies. It was very 

 noticeable at Lagos this year how the first shower of rain that fell 

 brought at once on the scene a considerable number of mosquitoes 

 where none were present before, just as if they had been unable to go 

 abroad without something to revive them. 



Doubtless it is in a great measure due to the long-continued 

 absence of rain, and to the nature of the soil, that there is so little 

 fever in many inland towns. The chiefs of some of them wish to 

 make out that they have no fever at all. Others admit that they lose 

 children by it. It is intended that the Medical Department should 

 make a sufficient number of observations on children at those places 

 to determine how far they are free from, or suffer from, fever. A 

 European town would probably have much more on the sites of these 

 native settlements on account of the freer use of water. The chiefs of 

 these inland towns unanimously state that they have no " blackwater 

 fever " there. 



