104 PRINCIPLES OF VETERINARY SURGERY 



lance as to render accurate deductions impossible. The mi- 

 croscopic examination alone would accomplish but little in 

 the study of bacteria. It is the study of the living germs, 

 their mode of life, their behavior in the media, the poisons 

 they elaborate, and the experimental inoculation of the 

 artificially cultivated bacteria that unfold their true patho- 

 genic powers and differentiate one from another. The 

 study of bacteria artificially grown in vitro, followed by their 

 expei'imental inoculation in vivo, has brought the science of 

 pathologic bacteriology to its present status. Numerous 

 mixtures have been used for the cultivation of bacteria, a 

 few of which have become standard preparations.. For the 

 pathogenic micro-organisms it seems essential that the 

 composition of the media approximate the juices of the 

 body. They should contain about 80 per cent of water and 

 be of neutral or feebly alkaline reaction. Transparency is a 

 desirable quality as it gives a better opportunity of observ- 

 ing the various changes which the media undergo under 

 the influence of bacterial growth. Solid media are prefer- 

 able to liquid under many circumstances, especially when 

 isolating the different varieties of bacteria and transplanting 

 them to fresh media until the bacterium has been passed 

 through several successive generations. The bouillon cul- 

 ture fluid is the artifice of Pasteur, while the idea of solid 

 media originated in the laboratory of Koch. 



All culture media must be absolutely sterilized as a 

 pre-requisite to the successful cultivation and isolation of, 

 bacteria. The materials from which they are made contain 

 bacteria that must first be eliminated. The feat is accom- 

 plished by boiling, steaming, chemicals, filtration, cold, 

 and by dry heat with the aid of specially improvised appa- 

 ratus. When thus prepared the media is transferred into 

 specially prepared, sterilized vessels and inoculated with 

 the infectious matter to be cultivated by means of the 



