of the most varied composition and of the most varied exposure 



in low places rich in water and organic substances, in soils of 

 volcanic origin, as well as in sedimentary soils of every geological 

 period, and even in soils composed of sandy quartz. Next to the 

 septic ferment the malarial ferment is, of all the disease-breeding 

 ferments, the most widely disseminated, and that which most 

 readily finds conditions suited to its development and propaga- 

 tion. What is this ferment ? Prof. Crudeli declares it to be an 

 organism, the microbe of malaria, the Bacillus malarice. This 

 organism dwells in the soil ; but a minimum temperature of 

 eS"" F., a certain amount of moisture, and the action of the atmo- 

 sphere on the soil in which it is contained are necessary for its 

 development ; so that it is possible to prevent its spreading by 

 interrupting the communication of the soil with the atmosphere, 

 either by covering it with water or by grasses the roots of which 

 would constitute, as it were, an impervious mat. 



" Prof. Crudeli remarks that sections of the city of Rome, which 

 weref covered by parks and gardens a few years ago, and which 

 were very malarious, have become very healthful, owing to the 

 lands being now covered by buildings and the new streets paved, 

 all contact of the air with the soil being thus shut off. 



" From the days of Varro it has been surmised that this ferment 

 was derived from a living organism ; but it was only in 1879 that 

 Crudeli and Klebs took up the investigation of a great number of 

 malarial soils, dry as well as marshy. They cultivated the very 

 smallest organisms found in these soils, experimenting with the 

 products of these cultures on animals ; analyzed the blood and 

 organs of men and animals infected with malaria, and established, 

 beyond all doubt, the existence of a living parasite. This parasite 

 attacks the red globules of the blood and destroys them after 

 having produced in them a series of characteristic alterations 

 which indicate with certainly the existence of malarial infection. 



" The effects of malaria are suspended by covering the ground 

 with buildings or by sowing the land in grasses, thus preventing 

 the contact of the atmosphere with the soil, and by drainage, that 

 is, by removing the moisture from the soil. 



" But, as man does not control the rain, it is evident that after a 

 rain even a drained soil will give off malaria, unless that soil is 

 cut off from contact with the atmosphere. In order to drain 

 certain portions of the Roman Campagna, the experiment has 

 been tried of planting trees that would absorb a great quantity of 

 water from the soil. With the preconceived idea that malaria is 

 due to putrid decomposition in marshy ground, it has been 

 proposed to make this attempt by means of the Eucalyptus. It 

 was thought that these trees of rapid growth would dry up marshy 

 lands and destroy, at the same time by means of the aroma of 

 their leaves, all miasmatic emanations. 



"Up to date (1886) not a single instance of hygienic improve- 

 ment by the sole means of Eucalypti has been ascertained, but the 

 possibility of so doing is not denied. It can be admitted that 

 these trees sometimes prove useful in certain malarial soils. I 

 frankly maintain, however, that frequently they 

 whatever, and that it is well to guard against 

 often blind the 



