NUTRIENT MEDIA. 17 



Beef-hroth. — Ten cubic centimeters of stiindurd beef ])r()tli inoculated 

 with a 1-nuu. loop of a fresh culture lliiid of the oruuiiisni was dis- 

 tinctly clouded in from four to eiohteen hours at a temperature of 35° 

 to 18° C. If the temperature was raisinl or loweretl throug-h several 

 degrees above or l)elow the limits indicated or if the inoculation was 

 made from a less active culture, the clouding- took place less rapidly. 

 Indeed, the clouding was delayed indetinitely by lowering the tem- 

 perature to 5° C. or by raising the temperature to 41° C. If the 

 beef broth was kept at room temperature (18° to 24^ C.) the organ- 

 ism remained alive for several weeks and a nearly white deposit 

 several millimeters in depth formed in the l)ottom of the tube. 



Aijar pJate cultures. — On the ordinary nutrient agar poured plates 

 made from a 24-hour-old beef-broth culture colonies were distinctly 

 visible in twenty-four hours at room temperatures of 18° to 20° C, 

 and plates made in the same way and kept at 30° to 35° C. showed 

 colonies distinctly in from tiftiMMi to eighteen hours. The form and 

 size of the colonies on the agar plates depended upon certain condi- 

 tions— e. g., if the colonies were numerous they ^vere small and round, 

 while if there were but few colonies in each plate they were some- 

 times round and sometimes radiating. They were usually radiating 

 if the plates were made from fresh cultures and kept at a temperature 

 of from 22° to 35° C. On the other hand, if the plates were made 

 from an old culture or if they were kept at an abnormally high or an 

 abnormallj' low temperature the colonies were round, even if there 

 were but few in each plate, Agar plate cultures made from Uschin- 

 sky's solution or broth cultures that had been kept dormant for sev- 

 eral months produced round colonies, but after a few transfers from 

 the dormant state to fresh media the a^ar plate cultures became char- 

 acteristically radiating (PI. II, figs. 2, 3, 4, and 5, and PI. Ill, fig. 1). 



The foregoing applies to the surface colonies, but in addition to 

 these there were some embedded colonies in practically all poured 

 plates. The embedded colonies were all spindle shaped unless viewed 

 end on, when they appeared to l^e round, with sharp, distinct out- 

 lines. They had a faint yellow tinge, and were nuich smaller than the 

 surface colonies. If the embedded colonies broke through the sur- 

 face, they spread out and behaved in the same manner as if they had 

 been originall}' surface colonies. (See the small colonies on PI. II, 

 figs. 2 and 5.) Some of the colonies lying at the extreme bottom of 

 the agar — i. e., between the agar and the ))ottom of the petri dish — 

 spread out, forming a thin layer which eventualh^ gave to the plate a 

 milky appearance when held up to the light. (See PI. II, fig. 2, and 

 PI. Ill, fig. 2.) The surface colonies, whether round or radiating, 

 had a shiny white surface and were only slightly opalescent. If radi- 

 ating, they usually had a central body, from which the branches radi- 

 ated (PI. in, fig. 1). The central body was more dense than the arms 

 or 1)ranches and the whole colony was slightly elevated above the sur- 

 27501— No. 60—04 2 



