604 REPORT OF THE COMMISSIONER OP AGRICULTURE. 



it wlien found. The descriptions of size, shape, and mode of staining 

 referred to cover-glass preparations made from the blood and the 

 internal organs directly. These characters change somewhat when 

 the bacterium is cultivated in artificial media. Thus the bacteria 

 grown upon potato vary slightly in size and appearance from those 

 obtained from meat infusions and from nutrient gelatine. On the 

 other hand, their appearance is the same whether the spleen of mice, 

 rabbits, guinea-pigs, or swine be subjected to microscopic examina- 

 tion. 



The microbe was characterized as a motile bacterium 1.2 to 1.5 

 inicromillimeters long and . 6 micromillimeter broad, growing readily 

 in neutralized and even slightly acid meat infusions, milk, on potato, 

 and gelatine which is not liquefied. During the past year the bacte- 

 rium has been studied very carefully, with a view to determine the 

 best means of preventing its multiplication, and thus preventing the 

 spread of the disease itself. The conclusions arrived at are given in 

 full below, but will be summarized from a practical point of view in 

 the chapter on prevention. 



Growth of the bacterium in simple hay infusion. — This was prepared by allowing 

 finely cut hay to soak in water for three or four days, filtering off the amber liquid 

 and sterihzing. Two tubes were inoculated with a drop from cultures in meat-in- 

 fusion peptone at different times. In both the foUowmg features were observed: 

 There was a slight turbidity witliin two days, which did not deepen perceptibly. 

 The bacteria were somewhat larger than in more nuti'itive liquids. In the shorter 

 forms there could be seen at each extremity more refrangent spherical masses, 

 while the central portions of the rod seemed empty. Longer rods contained three 

 or four of these bodies. "When stained they appeared darker than the rest of the 

 rod. They were consequently not spores, but very probably masses of protoplasm, 

 which had contracted into these globules, and which indicated a degeneration of 

 the bacteria. There were also forms present which were beaded, club-shaped, and 

 distorted. 



Though the acid hay infusion is not a suitable medium, yet the bacterium of 

 hog-cholera evidently multiplies in it to some extent, and we may infer that in 

 any organic infusions, such as are formed about pens among the food of swine, the 

 bacterium may multiply under the influence of a hot sun and be afterward taken 

 into the system with the food and water. 



Multiplication of the bacterium in water. — The hardiness of this 

 microbe is well illustrated by its capacity for multiplication in ordi- 

 nary drinking water. To determine this the following experiment 

 was made : 



September 8 : A culture tube containing very clear Potomac drinking water,* 

 which had been sterilized several weeks previous by a temperatiire above 110°C., 

 was inoculated from a pure culture of the bacterium. By mixing a given quantity 

 of tliis water immediately after inoculation with gelatine, and making a plate cult- 

 ure of the same, it was found that the water contained about 2G,240 bacteria in 1'='=. 

 The water was kept in the laboratory, in which the temperature corresponded 

 closely with that prevailing out-doors. It was examined from time to time on gela- 

 tine plates, and the number calculated for 1"=. The following figui'es give the 

 results obtained: 



September 8: 26.240 in l'^'^ (immediately after inoculation). 



September 9: 201.600 m !<=<=. 



Se])tember 10: 1.290.000 in 1". 



September 1 1 : Too numerous on plate to be counted. 



September 13: 2.608.200 in 1«. 



September 15: 1.519,560 in 1". 



September 17: 1,306,808 m 1". 



September 29: 83.700 in 1". 



October 12: 19,125 in 1«. 



* When drawn this water did not contain more than 100 to 200 bacteria to the 

 cubic centimeter. 



