122 Manual of Veterinary Jlicrobiology. 



2. 31ilk. 



Milk may be collected in a state of purity in ster- 

 ilized tubes by introducing a sterile canula into the 

 teat after the latter has been well disinfected. This 

 is the best means of obtaining milk free from germs, 

 but it is one which is not generally available, and, 

 most frequently, we are compelled to sterilize this 

 liquid. 



This is done in the autoclave at 115°. The milk, 

 without the cream, is then introduced into the Pas- 

 teur bulbs and subjected to the test of the incubator. 



3. Urine. 



It was in urine that Pasteur first cultivated the 

 bacteridium of charbon. The urine, after collection, 

 is rendered alkaline, filtered, and sterilized exactly 

 like the bouillon. It may be employed alone or after 

 the addition of supplementary nutritive substances. 



B. Solid media. 

 This consists of fluid media gelatinized, coagulated 

 blood serum, potatoes, etc. 



Gelatinized bouillons. 



Gelatinizing substances are added to bouillon, sim- 

 ple or complex, so as to render it solid and trans- 

 parent on cooling. The substances employed are 

 gelatin, gelose, Iceland moss, etc. 



Nutritive gelatin. — To the bouillon whilst in prepa- 

 ration and before boiling is added ten per cent of 

 gelatin. The fluid is passed through a cloth, neutral- 

 ized, and the process generally conducted as described 



