o 



112 CEOWN-GALL OF PLANTS. 



ALKALINE BEEF BROTHS. 



The organism grows letter in acid than in alkaline houillons. The 

 optimum reaction in peptonized beef bouillon lies between +12 and 

 + 24 of Fuller's scale. In May, 1908, growth was found to be more 

 rapid in + 15 bouillon than in phenolphthalein neutral bouillon. 

 This was true at end of the second and the eighth day. The inocula- 

 tions were from an agar culture 4 days old. 



This experiment was repeated in 1910 with +15 bouillon, neutral 

 bouillon, and — 15 bouillon. At the end of two days there was most 

 growth in the +15 and least in the —15. All showed more or less 

 clouding, es]:)ecially the alkaline ones. At the end of five days at 25 

 C. there was a plain white rim in the + 15 tubes, and a very scanty 

 one in the others; doubtfully present in some of the — 15 tulfes. On 

 shaking, the fluid was at least three times as cloud}^ in the + 15 

 bouillon as in the or — 15. The tubes were inoculated from 10 c. c. 

 of sterile water in which a loop from a 2-da,y agar culture was diffused 

 by shaking. For tests in other grades of alkalinity see following 

 table and the chart under Comparative Tests. 



SUGARED PEPTONE WATER. 



Heavy pellicle, long continued growth, and final hrown stain of the 

 fluid, in flasks of autoclaved river water containing Merck's c. p. 

 dextrose, V/itte's peptone and c. p. calcium carbonate. Frequently 

 the pellicle settled and a second one formed. The cultures were 

 alive at the end of 4 months when turned over to the chemist for 

 examination. 



MILK. 



Coagulation delayed; extrusion of whey begins 07dy after several 

 days; coagidum not peptonized (0- There is usually a j^ellicle or in- 

 terrupted pellicle. For example: Four tubes of sterile milk were 

 inoculated with a 1 -millimeter loop of beef-broth culture 3 days old 

 and kept at 23° C. Two da} s after inoculation no change had taken 

 place in the consistency of the milk. Six days after inoculation the 

 only change noticeable was the formation of a very shallow layer of 

 whey on the surface of the inoculated milk. This is the customary 

 behavior in milk. Often separation of whey is long delayed. 



In 6-months-old milk cultures, three-fourths dried out, but still 

 alive, the color of the gelatinous curd was Khamnin brown No. 2 

 nearly (Repert. de Couleurs, Soc. Fr. des Chr3'santh.), or between drab 

 and ocher of Standard Dictionary (spectrum). Under the micro- 

 scope, the bacteria were in the form of short rods, single and end to 

 end in pairs, mostly as a pure white precipitate, 3 mm. wide, which 



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