26 



In all of the gelatins liquefaction took place very slowly. In the 

 gelatins it seldom appeared earlier than the sixth day and often not 

 until after the fourteenth day (temperatures 13° to 18° C., 18° to 21° C, 

 and also 22° to 24° C), and nuich later on gelatins not so well adapted 

 to its growth. Even when once initiated the peptonization of the gda- 

 tins proceeded at such a snail's pace that 6 to 8 weeks usually elapsed 

 before the whole 1(> c. c. became fluid. This ver}" slow liquefaction 

 could not possibl}' have been due to the amount of gelatin used in my 

 cultures, since this varied from 8 to 15 per cent, or to the fact that in 

 preparing the media the gelatin was boiled only a verj^ short time so 

 as not to injure its solidifying properties. Neither does the tempera- 

 ture at which most of the experiments were made (8'-' to 21° C.) appear 

 to haA^e been the retarding cause, since liquefaction was not more 

 rapid at higher summer temperatures. To test this, a tube of stock 

 2-14c was inoculated in June, 1897, and left for some weeks at room 

 temperatures. These ranged from 25° to 34° C, the temperatures 

 nearl}" all of the time being above 27° C, and often for many hours 

 29° to 32° C, i. e., near the optimum for this organism. The folloAv 

 ing notes on such a culture may not be without interest: 



Stock 244c. — Tube of 10 c. c. inoculated June 14, noon, with a large loop from a 

 beef-brotli culture made June 3. Temperature, 25° C, gelatin fluid. 



June 15, 1 p. m. (temperature, 28° C. ). Feebly clouded throughout, no clouding 

 down from the surface on shaking. Not so cloudy as concomitant cultures of Ps. 

 pJiaseuU. 



June 16 (temperature, 29° C. ) : Much less cloudy than a corresponding tube of Ps. 

 pliaseoli. Hundreds of tiny zooglcete have gathered into the top layers of the fluid 

 gelatin and give to it, when shaken down, a granular appearance, 



June 17 (temperature, 28° C. ): Clear in comparison with a tube of Ps. phaseoH. 

 Growth largely in shape of small zoogloeae, some of which are agaiii gathering into 

 the top layers of the fluid gelatin. 



June 18 (temperature, 26° C. ): Very slowly increasing cloudiness with some tend- 

 ency of zoogloete to gather into top layers of the fluid gelatin. 



June 19, temperature 26° to 27° C. ; June 20, temperature 29° C. 



June 21 (temperature, 27° C): A pale yellow rim on the tube at the surface of the 

 gelatin. No pellicle, but some gathering of zoogloepe and individual rods into the 

 upper layers. Not mucli precipitate. On gentle shaking the fluid clouds down 

 from the surface. 



June 28 (temperature since last record, 25° to .31° C. ): A moderate amount of 

 yellow precipitate, much more than on the 21st. A copious yellow rim on the tube 

 at the surface of the gelatin. Gelatin nearly clear until gently shaken, when it 

 clouds down from the aggregation of germs in the surface layers. Numerous small 

 zooglcese still visible. On putting into ice water the gelatin soon became solid. 



July 8 (temperature since last record, 29° to 33° C. ; i. e., very hot summer weather) : 

 Body of the gelatin nearly clear. A decided rim of yellow on the walls of the tube 

 at the surface and some clouding of the upper layers of the gelatin. Considerable 

 yellow precipitate. The fluid clouds down on shaking. It still solidifies quickly in 

 ice water. 



July 29 (temperature since last record, 26° to 34° C. ): The gelatin has become 

 clear. There is a yellow rim on the walls of the tube above the surface of the fluid 

 and a copious yellow precipitate. The gelatin still solidities in ice water, but it is only 



