426 LETTER TO THE TDIE3. 



five days the remaining five were killed and ex- 

 amined. In the guinea-pig that died, and in the 

 three remaining infected ones, strongly-pronounced 

 tubercular disease had set in. Spleen, liver, and 

 lungs were found filled with tubercles ; while in 

 the two uninfected animals no trace of the disease 

 was observed. In a second experiment, six out 

 of eight guinea-pigs were inoculated with cultivated 

 bacilli, derived originally from the tuberculous lung 

 of a monkey, bred and re-bred for ninety-five 

 days, until eight generations had been produced. 

 Every one of these animals was attacked, while 

 the two uninfected guinea-pigs remained perfectly 

 healthy. Similar experiments were made with cats, 

 rabbits, rats, mice, and other animals, and, without 

 exception, it was found that the injection of the para- 

 site into the animal system was followed by decided 

 and, in most cases, virulent tubercular disease. 



In the cases thus far mentioned inoculation had 

 been effected in the abdomen. The place of inoculation 

 was afterwards changed to the aqueous humour of the 

 eye. Three rabbits received each a speck of bacillus- 

 culture, derived originally from a human lung affected 

 with phthisis. Eighty-nine days had been devoted 

 to the culture of the organism. The infected rabbits 

 rapidly lost flesh, and after twenty-five days were killed 

 and examined. The lungs of every one of them were 

 found charged with tubercles. Of three other rabbits, 

 one received an injection of pure blood-serum in the 

 aqueous humour of the eye, while the other two were 

 infected in a similar way, with the same serum, con- 

 taining bacilli derived originally from a diseased lung, 

 and subjected to ninety-one days' cultivation. After 

 twenty-eight days the rabbits were killed. The one 

 which had received an injection of pure serum was 



