THE WAR WITH THE MICROBES. 487 



others confirmed these ideas and came to similar conclusions in regard 

 to poisonous cheese. In 1856 Pannm asserted, as a result of his stud- 

 ies upon the poisons found in putrid animal matter, that these poisons 

 might be formed by some active plant cell, but their injurious effect 

 was independent of these cells. He demonstrated that fixed nonvola- 

 tile poisons could be extracted from putrid matter, which were soluble 

 in water and alcohol, not destroyed by heat, and produced the same 

 effects after they had been submitted to a high temperature as before. 

 These poisons he found to be intense in their action, 0.012 gram suffic- 

 ing to cause the death of a small animal. In 1866 Bence- Jones obtained 

 from the liver a substance which, with dilute sulphuric acid, gave a 

 bright blue fluorescence like that noted in similar solutions of quinine. 

 Probably this was the product of what we now call fluorescing bacteria. 



The work of Pasteur threw light upon the origins of these poisons. 

 As the ferment causes the alteration in the grape juice, so do micro- 

 scopic forms of life bring about the changes which take place in dead 

 animal and vegetable matter, and also those conditions in the living 

 body which we call disease. 



Many of these microscopic forms of single-celled plants, the bacteria, 

 have their natural habitat upon dead organic matter, but they may 

 flourish in the living body, and are almost unlimited in variety, appear- 

 ance, and behavior. It is possible also to cultivate them upon specially 

 prepared solutions, after their individual peculiarities have been studied. 

 Some thrive best in light, others in darkness; some like a goodly sup- 

 ply of oxygen, others prefer nitrogen : some are very sensitive to changes 

 of temperature, while others readily accustom themselves to vicissitudes. 



These different bacteria further are somewhat eccentric within as 

 well as without the animal body. Some, as the diphtheria germs, find 

 their most comfortable habitat upon certain mucous membranes, others 

 in the lungs, some in the digestive tract, still others in the blood, while 

 others again confine themselves to certain external cells and membranes. 

 In their artificial cultivation this eccentricity is equally apparent. 

 While nearly all thrive upon beef broth, some prefer the beef broth 

 with an excess of acid, others with an excess of alkali. Some demand 

 the addition of sugar or glycerine, others the addition of sugar together 

 with acid, while some are satisfied with a diet of phosphates, salt, and 

 water. These peculiarities have to be studied for each germ, and while 

 many can accommodate themselves to their surroundings, and while 

 the same germ grown upon different media produces the same sub- 

 stances, the amount of each substance is a varying one, and in cultiva- 

 ting them artificially we must find which diet gives rise to the largest 

 amount of the most active jn'oducts. 



Shortly after the work of Panum just referred to, the Italian chemist 

 Selmi outlined methods of extracting poisonous principles from dead 

 animal matter, and gave to these substances the name ptomaines, on 

 account of their origin. Later, in 1876, the first analysis of a ptomaine 

 was made by Nencki and its formula determined. Further experiments 



