136 Manual of Veterinary Microbiology. 



resented bj small raised droplets of a oily appear- 

 ance and of various colors: white, yellow, rose, red, 

 purple. In some cases they appear as depressed 

 points with regular or sinuous borders; sometimes, 

 again, we see a felted mass of filaments radiating 

 around a center. Certain germs fluidify the gelatin 

 and thus produce a conical depression, full of fluid, 

 in the substance of the medium. 



When these colonies are examined under a low 

 magnification their surface is seen to be sometimes 

 smooth, sometimes granular, their contour regular or 

 sinuous, occasionally bristling with filaments. All 

 these are peculiarities which serve to distinguish the 

 various pathogenic species. 



In gelatin tube-cultures, if the inoculation has 

 been made by puncture through the mass, the inocu- 

 lation track may be seen to become turbid and grad- 

 ually increase in size; sometimes the germs also 

 grow on the surface of the gelatin and spread them- 

 selves out in such a w^ay that the whole assumes the 

 shape of a nail. When the growth fluidifies the gel- 

 atin around the inoculation track the space which it 

 occupies takes the form of a funnel ; but it also hap- 

 pens that liquefaction occurs progressively by zones 

 from the surface toward the deeper parts. Although 

 the inoculation is made in a continuous track the 

 growth may only appear in isolated points; this oc- 

 curs when only a small number of germs have been 

 sown. From the inoculation made into the depth of 

 the gelatin a series of tufts may radiate outward, 

 thus giving the culture the appearance of a cylindri- 

 cal brush or sw^ab. 



Cultures upon the other solid media may present 



