This interesting question has been often asked, and frequently answered, though not in a manner which has been considered satisfactory. Profs. Klebs, of the University of Prague, and Tomassi-Crudeli, of the University of Rome, have together conducted an investigation of the malaria of the Roman Campagna, with the following conclusions:

1. The poison of malaria is met with in malarious localities even during the season when man does not contract malarial disease.

2. At this season of the year the poison is found in the layers of the air in contact with the surface of the ground in malarial sections. The experimenters collected the poison by means of powerful blowers by which large quantities of air were forced against the surface of glass smeared with glycerine, in which the poison was caught and retained.

3. Large quantities of water hinder the development of malaria.

4. The poison of malaria is a distinct organism, belonging to the genus bacillus. It is found in the soil of malarious regions in the form of minute spores.

5. When the malarial spores or germs are received into the system of an animal, they develop into long filaments which separate by transverse division into shorter filaments, new spores being developed at the points of division. The organism has been named bacillus malaria.

In experiments upon animals, the observers found that liquids containing the spores described, when injected into the blood of rabbits, produced malarial fever possessing the characteristics of remittent fever in man, causing great enlargement of the spleen,-commonly known as ague-cake in human beings,-together with increase of coloring matter in the spleen and other parts of the body. When, the liquid was filtered before injection, so as to remove the spores, no such results were observed.

The effects of this poison whatever it may be, are far more serious than is generally supposed. When a person has been long exposed to the influence of malaria, a sort of tolerance on the part of the system may be established, so that active symptoms of malarial poisoning may not appear, though the evil effects are still being wrought.

Chronic Malarial Poisoning is a very common condition in malarial districts. It is generally indicated by a peculiar sallow complexion, general debility, dyspepsia, enlargement of the liver and spleen, greater or less degree of mental depression, and various other disturbances of the system. In malarious countries, almost every disease is complicated with the effects of this poison. The idea which many people have entertained that malaria in some way acts as a curative for consumption, has no foundation whatever.