106 EEPORT OF THE BUEEAU OF ANIMAL INDUSTBY. 



It may "be argued that bacteria obtained in this way may be acci- 

 dentally present in the diseased lung tissue, and that the bacteria 

 which are the re.al cause may not produce any disease whatever in 

 the experimental animals. Without entering at present into any 

 detailed statement of the other arguments in favor of this bacterium 

 as the cause of swine plague we may state that most of the bacteria 

 which produce diseases in the higher animals are fatal to mice or 

 rabbits or guinea pigs, or a}l three. We need only to mention anthrax, 

 black quarter, tuberculosis, fowl cholera, rouget among swine, hog 

 cholera, glanders, the German swine plague, and infectious pneumo- 

 nia in horses. And the converse may also be assumed as true that 

 any bacteria which are harmless to these experimental animals are, 

 as a rule, not the cause of virulent diseases among higher animals. 



In one of the cases given in the preceding pages in which the dis- 

 ease had involved the pleura, pure cultures of this bacterium were 

 obtained from pleural effusion, while it was obtained from the lung 

 tissue by inoculating rabbits with bits of the tissue as above described. 

 This case, therefore, is worth a host of negative ones, for we can not 

 but believe that if the disease enters a closed cavity, like that of the 

 thorax, the bacterium there found exclusively is the cause of the 

 process. In a subsequent case the same organism was obtained from 

 the diseased pleura, but mingled with two others, a chromogenous 

 bacillus found in cases of hog cholera several years ago, entirely 

 harmless, and the streptococcus already mentioned. The lungs in 

 this case emitted an unpleasant odor. 



The streptococcus was isolated after much difficulty and more carefully examined. 

 It requires a higher temperature for its growth on gelatine, so that plates made 

 during the winter months were as a rule unsuccessful. It grows quite well in 

 nutrient gelatine at a temperature of 75 to 80 F. The colonies in the depth of 

 the gelatine are spherical, whitish; the surface growth is very scanty. In liquids 

 the growth is quite peculiar. The culture liquid remains entirely clear, but a num- 

 ber of white flakes appear usually in the bottom of the tube, "occasionally on its 

 side when the tube remains in an inclined position. These flakes do not grow 

 larger than 1 to 2 millimeters in diameter. Under the microscope they are seen to 

 consist of masses of interlacing chains of cocci. This accounts for the permanently 

 limpid condition of the culture fluid. It serves at the same time as an important aid 

 in determining the purity of a culture. This description applies to beef infusion. 

 When 1 per cent, peptone is added the flakes are much larger and the deposit be- 

 comes quite abundant. The liquid remains clear. They do not grow on potatoes. 



When milk is inoculated its appearance remains unchanged. 



In sections of the lung tissue they are brought out very neatly by Gram's method, 

 and the chains can be readily followed by f ocusing as they wind through the cel- 

 lular exudate in the alveoli. This property of retaining a deep-blue color after the 

 application of iodine solution is retained by the cocci when under cultivation. The 

 individual cocci are slightly oval, the longer diameter being about .8 micrpmilli- 

 meters. They strikingly resemble the bacteria causing swine plague in exhibiting 

 two stained extremities joined together by a median, unstained, very narrow zone. 

 They are, however, very readily distinguished from swine plague bacteria. The 

 latter are much smaller, do not retain the stain when treated according to Gram's 

 inetbdd, and never appear in chains. The uncolored zone may be looked upon as 

 a stage in the process of division of a single coccus into two cocci. 



The pathogenic power of this organism was tested by inoculating one-twelfth cubic 

 centimeter of a pure, liquid culture subcutaneously into two rabbits and two mice. 

 Both mice were found dead on the morning of the second day. One, being partially de- 

 composed owing to the heat during the night, was not examined. In the other there 

 was at the point of inoculation a slight, reddish, serous infiltration containing numer- 

 ous streptococci. There were a moderate number in the spleen and blood from the 

 heart. In a gelatine tube culture made from the latter a number of colonies of 

 streptococci appeared after a few days. In the beef infusion tube a small number 

 of minute white niaSSes appeared after three days, floating in -a -perfectly limpid, 

 liquid. 'These were made up of interlacing chains of cocci. The two rabbits re- 

 mained well. When killed after fifteen days one of them was found infested with 



