DISCOVEEY OF THE TUBERCLE BACILLUS. 427 



found perfectly healthy, while the lungs of the two 

 others were found overspread with tubercles. 



Other experiments are recorded in this admirable 

 essay, from which the weightiest practical conclusions 

 may be drawn. Koch determines the limits of temper- 

 ature between which the tubercle bacillus can develop 

 and multiply. The 'minimum temperature he finds 

 to be 86 Fahr., and the maximum, 104. He con- 

 cludes that, unlike the Bacillus anthracis of splenic 

 fever, which can flourish freely outside the animal 

 body, in the temperate zone animal warmth is neces- 

 sary for the propagation of the newly-discovered 

 organism. In a vast number of cases Koch has 

 examined the matter expectorated from the lungs 

 of persons affected with phthisis, and found in it 

 swarms of bacilli, while in' matter discharged from 

 the lungs of persons not thus afflicted he has never 

 found the organism. The sputum in the former cases 

 was highly infective, nor did drying destroy its 

 virulence. Guinea-pigs infected with expectorated 

 matter which had been kept dry for two, four, and 

 eight weeks respectively, were smitten with tubercular 

 disease quite as virulent as that produced by fresh 

 expectoration. Koch points to the grave danger of 

 inhaling air in which particles of the dried sputa of 

 consumptive patients mingle with dust of other 

 kinds. 



The moral of these experiments is obvious. In 

 no other conceivable way than that pursued by Koch 

 could the true character of the most destructive 

 malady by which humanity is now assailed be de- 

 termined. And however noisy the fanaticism of the 

 moment may be, the common-sense of Englishmen 

 will not, in the long run, permit it to enact cruelty 

 in the name of tenderness, or to debar us from the 



