180 APPENDIX. 



Origin. A disease affecting cattle and giving rise to tubercle- 

 like lesions in the lungs, liver, and spleen. Common in France. 



Form. Small interwoven mass of threads arranged in tufts 

 found in the centers of the tubercles. 



Culture. At body-temperature in various media. 



Bouillon. Colorless masses irregular in size and shape. 



Agar and Gelatine. Small, rounded, opaque colonies, thicker 

 at the periphery. 



Potato. Rapid growth of pale yellow dry scales, consisting of 

 many spores. 



Pathogenesis. Pure cultures introduced into the peritoneum 

 of guinea-pigs give rise in 9 to 20 days to tubercle-like lesions. 

 Subcutaneous injections cause abscesses with secondary in- 

 volvement of the lymphatics, ending in recover} 7 . Dogs, 

 horses, and rabbits are immune. 



Staining. Wright's double stain for tissues; also Gram's. 



Examination of Air, Soil, and Water. 



Air, Many germs are constantly found in the atmosphere 

 about us. Bacteria unaided do not rise into the air and fly 

 about ; they usually become mixed with small particles of dirt 

 or dust and are moved with the wind. The more dust the more 

 bacteria, and therefore the air in summer contains a greater 

 number than the air in winter, and all the other differences can 

 be attributed to the greater or less quantity of dust and wind. 



Methods of Examination. The simplest method is to ex- 

 pose a glass or dish covered with gelatine in a dust-laden 

 atmosphere or in the place to be examined. In the course of 

 24 to 48 hours colonies will be seen formed wherever a germ has 

 fallen. But this method will not give any accurate results in 

 regard to the number of bacteria in a given space ; for such a 

 purpose somewhat more complicated methods are needed, so 

 that a certain amount of air can come in contact with the 

 culture media at a certain regulated rate of speed. 



Hesse's Method, This is the most useful of the various 

 methods in vogue. 



A glass cylinder, 70 centimetres long and 3.5 centimetres in 

 diameter, is covered at one end, by two rubber caps, the inner 



