PRINCIPLES OF VETERINARY SURGERY 105 



sterilized platinum needle, pipette or other instrument. 

 When the infectious matter is inoculated into a solid or 

 semi-solid medium, the name stab-culture is applied, and 

 when spread over the surface the process is designated as 

 amear-culture. 



The mixture thus inoculated is then submitted to a tem- 

 perature which must vary according to the particular 

 requirements of the micro-organisms under investigation, 

 which is usually 37° C. The incubator is usually necessary for 

 this purpose, as by its use the temperature can be changed 

 or maintained at a certain degree of heat at will. Often 

 cultures will grow well in ordinary temperatures of a room, 

 but high temperatures, — blood heat, — are more favorable to 

 the exuberant growth of bacteria in artificial media. 



At a given time, varying with each particular bacterium, 

 the macroscopic and microscopic developments furnish im- 

 portant revelations for differentiation. The medium may be 

 peculiarly changed, may emit a special odor, may be lique- 

 fied or not, may be cloudy or clear, may contain a precipi- 

 tate, or finally it may have developed a characteristic color. 

 An accurate knowledge of these macroscopic changes is no 

 small part of the successful investigator's attainments. A 

 subsequent microscopic examination of the microbian flora 

 of the culture, the inoculation of fresh cultures to obtain 

 new generations of the microbe, and finally inoculation ex- 

 periments upon living animals completes the investigation 



The anaerobic bacteria must be cultivated in the absence 

 of free oxygen. This is accomplished by excluding air, by 

 means of various mechanical devices, by cultivating them 

 in the presence of inert gases — hydrogen — or by creating a 

 vacuum in the container. 



The more common culture media are bouillon, po- 

 tato, agar-agar, and blood-serum. Gelatin, gelose, milk 



