104 



stained in an aqueous solution of methyl violet, the bacteria appear 

 as elongated ovals, or short rods, with rounded ends, chiefly in pairs. 

 In cover-glass preparations from the spleen, when the staining has 

 been very brief, only the border of the rods is deeply stained, the 

 central portion being pale. When the period of staining is prolonged 

 the rod may become uniformly stained. Bacteria thus prepared and 

 mounted in balsam measure from 1.2 to 1.5 micro-millimeters in 

 length and about 0.6 micro-millimeters in breadth. The germs have 

 not been positively identified in the ulcers of the intestines by micro- 

 scopical investigations, but their presence has been demonstrated by 

 the inoculation of mice and rabbits. 



Staining of hog-cholera hacteiia. — CoA^er-glass preparations are 

 stained by a few minutes' contact with watery solutions of the ordi- 

 nary aniline colors, such as methyl violet, fuchsin, and methylene 

 blue. 



Distfihiition of hacteria in the Ijody. — In acute cases the spleen con- 

 tains the largest number, the liver nearly as many. The lungs, lym- 

 phatic glands, and kidneys contain a moderate number. They are 

 fewest in tlie blood from the heart. In chronic cases the number in 

 the internal organs is very small. 



Biology of the hog-eliolera hacillas. — This section gives the diag- 

 nostic characters as obtained by studying the growth of the bacillus 

 in and on the different culture media. 



The diagnosis of hog cholera hy means of inocidation. — There are 

 given here the results obtained by inoculating mice, rabbits, guinea- 

 pigs, and pigeons with the bacilli of hog cholera. 



Vitality of hog-cholera hacilli and their resistance to various 

 destructive agents. — The vitality of these bacilli in cultures remains 

 for months unchanged. 



Resistance of hog -cholera hactei'ia to heat. — The bacilli are de- 

 stroyed by momentary exposure to boiling water. The temperature 

 of 136° F. to 138° F. destroys them when moist in fifteen minutes, 

 and 130° F. in one hour. A dry heat of 176° F. destroys them in 

 fifteen minutes. They retain their vitality after freezing. 



Vitality of hog-cholera Ijacteria in ordinary water. — Experiments 

 are given to show that these germs multiply for some days after they 

 are j^laced in ordinary water, and that some of them retain their 

 vitality for about two months. 



Resistance to drying at ordinary temperature. — When culture 

 liquids are dried upon cover-glasses and upon threads the bacilli 

 lose their power of multiplying in from ten to fifty days. "N'N^ien 

 small bits of spleen tissue were rubbed on cover-glasses and dried 

 the germs were capable of multiplying for four months. When a 

 moist and dry state alternated the germs which resisted drying four 

 months were destroyed in less than one month. 



Length of time during which virus remains (dive in the soil. — A 

 number of experiments were made by infecting soil' and inoculating 



