INTRODUCTION 



The poisonous principles contained in the plants described 

 in the following pages are now known to exist even under 

 cultivation, although cultivation may modify their virulence; 

 and exposure, also, to the influence of heat, acids, or anti- 

 septics, would seem in many cases to render the toxin inert. 



Sea-water, or the iodine contained in it, appears to be 

 incompatible to vegetable toxins ; and it is an interesting and 

 significant fact that iodine, besides being antagonistic to very 

 many, of the alkaloids, will destroy most Micro-Fungi and 

 those of the Bacteria which cause infectious disease. 



Among Micro-Fungi the Pyrenomycetes, Carpomycetes, and 

 Oomycetes need a living host, which they have the power of 

 selecting — i.e., Puccinia graminis selects Wheat and Barbery, 

 while P. coronata prefers Grass and Buckthorn. Pencillium 

 and Aspergillus, however, will thrive equally on living or dead 

 organic food-material. 



The virulence of the microscopic plant causing Glanders 

 {Bacillacece) is increased when grafted from the horse to man, 

 just as the mistletoe-plant thrives best when artificially 

 grafted from one species of tree to another. 



Again; since all Bacteria have come from a common 

 ancestor, we assume certain ultra-microscopic forms which 

 have become acclimatised to mankind; and we must, for the 

 present, suppose these forms to be m the nature of a ferment, 

 or enzyme, produced by the Bacterium. 



The affection known as Dengue is caused by one or more of 

 these ultra-microscopic ferments. Pellagra will ultimately 

 prove to be due to vitamin deficiency, and not to the fungus 

 Pencillium glaucum. Sprue, on the other hand, is almost 



