INFECTIOUS DISEASES AND MICROBES, ETC. 219 



that B. malaria has been called 'an earth-born 

 poison.' 1 This microbe is said to be heavier than 

 most gases, ' and scarcely floats six feet above the 

 ground ; it may be wafted some distance by winds, 

 but mountains hold it back, and belts of trees, 

 especially the eucalyptus, destroy its efficacy.' 



Gubler 2 and many others have shown that the 

 eucalyptus or ' fever-destroying ' tree has consider- 

 able power in destroying the microbe of malaria, 

 this being due to the action of the aromatic gases 

 given off by the tree. One instance may be cited 

 of the fever-destroying properties of the eucalyptus. 

 ' In a desolate part of the Campagna there stands an 

 old monastic institution upon a spot consecrated by 

 tradition as that whereon St. Paul was martyred. 

 For centuries this part of the Campagna [Tre Fon- 

 tane 3 ] was a stronghold of pestilential fever, and 

 prolonged residence in the monastic institution in 

 question surely led to death. Some few years ago 

 a band of Trappist monks planted the eucalyptus in 

 its cloisters, and the trees have since grown to a 

 great height. What is more important, however, is 

 that the place is now once more habitable, and fever, 

 it is said, reigns there no more.' 4 There are also 

 plantations of the eucalyptus in Corsica, Algeria, 

 Italy, California, Australia, and other parts of the 

 world ; and there is little doubb that these trees are 

 antagonistic to the spread of malaria, because the 



1 Felkin in Proc. Roy. Soc. of Edinburgh, vol. xvi. p. 269. 

 - Journal de Pharmacie et de Chimie, 1871. 



3 Known anciently as Aquae Salvise. 



4 Kingzett's Nature's Hygiene (3rd ed.), page 266; see also 

 Giglioli's Fermenti e Microbi, pp. 247-257. 



