One reason why the mosquitoes were not earlier associated with these diseases was that all who investigated the matter at all turned their attention to the bad condition of the air in these swampy regions. Malaria means bad air. We all know that we can see the mists arising from such regions, particularly in the evening or at night, and as exposure to these mists very often meant an attack of malaria they were naturally supposed to be the cause of the disease. So for a long time the whole attention of investigators was turned toward studying and analyzing these vapors, and various experiments were made which seemed to show conclusively that the malaria was caused only by these emanations. The investigations even went so far that the exact germs that were supposed to cause the fever were separated and experimented with. THE PARASITE THAT CAUSES MALARIA The blood had been studied time and again and the characteristic appearance of the blood of a malarial patient was well known. In 1880 Laveran, a French army surgeon in Algiers, began to study the blood of such patients microscopically and soon was able to demonstrate the parasite that caused the disease. His discoveries were not readily accepted, but other investigations soon confirmed his observations and the fact was gradually firmly established. Not until recently, however, did this distinguished physician receive a full recognition of his work. A few years ago he was awarded the Nobel prize for medicine, perhaps the highest honor that can be bestowed on any physician. It is interesting, too, to note in this connection that it was another French surgeon who in 1840 discovered that sulphate of quinine is a specific for malaria. [Illustration: FIG. 96--Horse and cattle tracks in mud filled with water; good breeding-places for Anopheles.] [Illustration: FIG. 97--A malarial mosquito (_Anopheles maculipennis_); male.] [Illustration: FIG. 98--A malarial mosquito (_A. maculipennis_); female.] The next important step was made in 1885 by Golgi, an Italian, who studied the life-history of the parasite in the blood and distinguished the three forms which cause the three most familiar kinds of malarial fevers, the tertian, the quartan and the remittent types. From this time on this parasite has been studied by physicians of many nationalities and the whole course of its life-history worked out. In order that we may understand how it was that mosquitoes were determined to be the means of disseminating this parasite we will discuss first its life-history in the human blood. The parasites that cause the malarial fevers are Sporozoans and belong to the genus _Plasmodium_. Other names such as _Hæmamoeba_ and _Laverania_ have been used for them, but the term _Plasmodium_ is the one now most commonly employed. The three most common species are _vivax_, _malariæ_ and _falciparum_, causing respectively the tertian, quartan and remittent fevers. LIFE-HISTORY OF PARASITE