150 APPENDIX. 



ening, purulent collections form and the normal structure is 

 destroyed. 



The usual seat is in the maxillary bones, but the fungus has 

 been found in the lungs, tonsils, intestines, and various other 

 organs in man and cattle. 



Examination. Well seen in the unstained condition. From 

 the pus or scraping a small portion is taken and squeezed upon 

 the glass slide ; if calcareous matter is present, a drop of nitric- 

 acid will dissolve the same. 



Glycerine will preserve the preparation. 



Staining. Cover-glass specimens stained best with Gram's 

 method. Tissue sections should be stained as follows : 



Ziehl's carbol-fuchsin, ten minutes. Rinse in water. 



Cone, alcohol sol. of picric acid, live minutes. Rinse in water. 



Alcohol, 50 per cent., fifteen minutes. Alcohol absolute, clove 

 oil, balsam. 



The rays stained red, the tissue yellow. 



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 



