3IALAEIA AND MOSQUITOES 61 



There was no autochthonous case of malarial fever for 

 years at the League Ishuid Navy Yard, although there 

 was a distinct breeding-g-round for Anopheles near by. 

 Woldert has caught larvte of Anopheles in a clear pool of 

 water in the Pocono Mountains of Pennsylvania, a notable 

 health resort, at an elevation of three thousand feet above 

 sea-level. The statements that malaria has prevailed when 

 there were few or no mosquitoes are alwaj's too vag'ue to 

 be of value, because it is not definitely stated whether the 

 cases were relapses or fresh infections. In cases where 

 mosquitoes are numeroiTS, moreover, and there is no mal- 

 aria, to the point aaIiIcIi we have already made that prob- 

 ably no malaria has been broug'ht into the vicinity may 

 be added the fact that when mosquitoes are numerous, 

 almost without exception they are found to be the com- 

 mon species of Culex, which, as shown, have nothing to 

 do Avith malaria. It is often stated, for example, that 

 malarial fever is caused by excavating the ground ; newly 

 turned earth is said to be responsible for it, but, as a 

 matter of fact, as pointed out by Ross, there are millions 

 of people constantly engaged in digging Avithout suffering 

 from the disease more than do others, and then also ex- 

 cavations always result in surface pools of water, m Avhich 

 for a time Anopheles will frequently be found breeding. 

 One curious case has been mentioned by Mr. D. E. Hutch- 

 ings, in the English journal, Natiwe, in which he stated 

 that he knew of a medically authenticated case of malaria 

 having been caused by fresh earth carried past a window 

 in buckets by coolies. This statement is criticized by 

 Ross in the following words : " Which fact was medically 



