BACTEBIAL DISEASES OF MAX AN]) ANIMALS 95 



1. Examine and make descriptions of cultures of B. tul>er<-u- 

 lorist on the general table. Compare cultures of bovine and 

 human tuberculosis. 



2. Examine and describe the museum preparations of patho- 

 logical material on the general table. 



3. Observe the post-mortem conditions of a tuberculous guinea 

 pig. In what parts of the body are tubercles most abundant ? 



4. Select one of the small tubercles or a portion of a diseased 

 organ, ({rasping it with the dissecting forceps, cut it off. 

 Smear the freshly cut surface over the central portion of a 

 glass slide. Dry and fix as usual. Stain by the Ziehl-Neelson 

 method and counterstain with methylene blue. Do not put a 

 cover glass over the smear. Wait until the water has evapo- 

 rated ; then put immersion oil on it and examine directly with 

 the oil-immersion objective. The tuberculosis organisms should 

 appear as slender rods stained red ; the body cells are stained 

 blue. If the preparation is not satisfactory, repeat until a good 

 one is obtained. 



5. Draw a field showing the relation of the B. tulH'rculoxix to 

 the cells and tissues. 



6. Read and become familiar with the modern principles of 

 treating tuberculosis in man. Has tuberculin any remedial 

 value in treating the disease ? 



Exercise 135. Green Pus 



Green or blue-green pus is formed sometimes on surgical 

 dressings, due to the- development of B. pi/o<-i/n<>ux. In many 

 of its characters this organism closely resembles B. fliwrwrux 

 Ufjuefaciem, but it has been shown unquestionably to be patho- 

 logical both in pure and in mixed infections. 



The deep-blue pigment, pyocyanin, has been isolated and 

 studied chemically. It is not toxic to animals. The toxin is 

 very resistant to heat. The virulence of the organism may be 

 inferred from the statement, made by Jordan, that one tenth of a 

 loop of a fresh agar culture will kill a guinea pig in twenty-four 

 hours. 



