316 POPULAR SCIENCE MONTHLY. 



propriate species of mosquito belonged to the genus anopheles. There 

 can not be the slightest doubt that the mosquito acts the part of trans- 

 mitting agent as well as definitive host of the malarial parasite. 



This is a piece of knowledge of the utmost importance to mankind, 

 for we know that malarial disease in tropical countries — which, after all, 

 in the future will be the most important parts of the world, seeing that 

 they can produce more food than temperate countries and can therefore 

 support a larger population — causes more deaths and more disposition 

 to death by inducing cachectic states predisposing to other affections 

 than all the other parasites affecting mankind put together. We know 

 now in what way this parasite is acquired. Depend upon it, in time, 

 in virtue of this knowledge, we will get enormous power over the 

 disease and sooner or later we will be able to prevent the infection of 

 man by the parasite. It is only a question of study and the application 

 of the knowledge already acquired, only a question of money and per- 

 severance and a little ingenuity, and these results will come. It may 

 not be in ten years or twenty years, but sooner or later the energies 

 of a considerable portion of scientific mankind now being expended in 

 endeavoring to devise means for preventing the infection of men with 

 the malarial germ by the mosquito will bear valuable fruit. 



You can readily understand that it is of great importance to be 

 able to recognize the special species of mosquito which convey malaria. 

 The effective species as regards human malaria belong to the genus 

 anopheles; species of the genus culex are effective in the case of 

 sparrow malaria. Fortunately, these two genera are easily recognized 

 even by the amateur zoologist. If you find a mosquito clinging to the 

 wall or other surface you can tell which genus it belongs to by its 

 posture. If the body is stuck out nearly at right angles to the surface 

 on which the insect is resting, it is an anopheles. If the body is almost 

 parallel to the surface, it is a culex. There is another test which is 

 easily applied if you have a pocket lens; in culex the two organs known 

 as palpi are rudimentary and very short; whereas in anopheles those 

 organs are almost as long as the proboscis. It should be remembered 

 that the male mosquito is not a blood-sucker and therefore is not dan- 

 gerous. It is the female anopheles which transmits the disease. The 

 mosquito larvae inhabit stagnant or slow-running water. If a mosquito 

 larva be found with its head downwards, the body hanging at right 

 angles to the surface of the water, it is a culex; if the body lies parallel 

 to the surface of the water, it is an anopheles. There are other points 

 of difference with which I need not now trouble you; those referred 

 to suffice for diagnosis between the innocuous and the dangerous 

 mosquitoes. 



The facts regarding the malaria parasite which I have described 

 are of great importance for many reasons. First, because they help 



