PRINCIPLES OF VETERINARY SURGERY 95 



depth of a solid culture media, a covered vessel, or deeply in 

 the recesses of the living tissues. Examples, bacillus 

 aerogenes capsulatus, bacillus oedematous maligni, bacillus 

 anthracis symptomatici, etc. 



d. The formation of acids is the property of many micro- 

 organisms. Acetic, lactic and butyric acid fermentation is 

 created in the culture media by bacteria bearing the names 

 of these acid products. In most instances the generation 

 of acids continues until the media becomes untenable for 

 further grow^th of the microbes, w^hich then die in their own 

 products. 



e. Chromogenic bacteria are color producing bacteria. 

 These micro-organisms are largely non-pathogenic, yet some 

 are capable of producing disease. The various pigment- 

 forming bacteria are capable of producing practically all of 

 the known colors, red, yellow, black, green, blue, lemon, etc. 

 Examples, staphylococcus pyogenes aureus, bacillus pyocy- 

 aneus, bacillus prodigiosus, etc. 



f. Photogenic and Other Bacteria. — Besides the roles 

 played by the preceding classes of bacteria, photogenesis 

 and other functions might be enumerated, but these are of 

 but minor import in the special study of surgery. The 

 production of phosphorescence — light — is the property of 

 numerous micro-organisms, notably the bacillus phosphor- 

 escens. The light-producing property is often so active 

 as to dimly illuminate the interior of the incubator. 



g. Pathogenic bacteria, or disease producing bacteria, 

 are the most important of the micro-organisms to the 

 pathologist. All other forms are included in the great group 

 called non-pathogenic bacteria. A distinct line of demarca- 

 tion cannot, however, be drawn between these two groups. 

 Some bacteria are pathogenic to all warm blooded animals 

 and yet incapable of producing any derangement in the cold 

 blooded. Some will kill in a certain genus and prove per- 



