19 



Further, this bacillus was repeatedly isolated from the secretions of the 

 hens and pigeons which had been inoculated with it. At first, it was usually 

 •present in the tumors of the submucous or subcutaneous tissue in pure culture. 

 Later, it was found mixed with other bacterial forms in the tissues and also 

 in the exudation products. In chronic cases of the disease, the roup bacillus 

 could not be culturally detected, but it could often be identified microscopically 

 in the cheese-like masses of diseased or inoculated fowls. We have never 

 isolated this bacillus from the blood or other internal organs. 



Morphology of B. Cacosmus. 



The roup bacillus is a small rod .25 to sm.m.m. thick, .25 to 5m.m.m. long, 

 with rounded ends. It often occurs in pairs and occasionally in short chains of 

 4 or 5 cells. The smallest forms are coccus-like, the longer are rods. With the 

 ordinary aniline stains, they stain very well. In old bacilli, there are often 

 only zones or parts of the cell that take the stain (involution forms). The 

 bacteria are not stained by Gram's method. In young agar or bouillon cul- 

 tures, the roup bacilli are very motile. They possess 4 or 5 peritrichous cilia 

 which are three or four times as long as the bacilli. Capsules and spores are 

 not formed. 



Ctltubes. 



Gelatine Plate Cultures. Colonies appear in 24-28 hours as small, round. 

 iridiscent points, which grow slowly. They are flat, round, or somewhat irregu- 

 lar in shape. They never become prominent ; but, as their growth continues. 



Fig. 20.^ From the nasal secretion 

 of hen 11 and 2ti. Ciliated cell 

 showing slimy degeneration. 



Fig. 21. — Bodies from a tumor 

 from hen No. 17. 



they sink deeper into the gelatine. The surface is smooth and shining. They 

 are light grey in color. Through the microscope, young colonies are seen 

 to be slightly granular. The centre is dark, yellowish or brown, the border 

 zone clearer, and usually provided with darker, radiate markings ; m older 

 colonies, these disappear, and the gelatine becomes liquefied to the bottom of 

 the plate. The growth at the edge of the colony lasts for about 8 days, and 

 then ceases. In t'his time, they usually reach the size of from 3-5 mm., while 

 after two days fhey were from 1-2 mm. in size. The submerged colonies ap- 

 pear as round, slightly granular, clear points, which quickly penetrate to the 

 surface of the gelatine. 



