21 



all were kept in the dark at room temperatures. Daring the first 5 

 days the temperature ranged from 23"-^ to 31^ C. ; during the next 20 

 days the range was from 22^ to 3-i^ (25^ to 30^ most of the time), and 

 during the hist () days, from 29^ to 37^ C. 



Hesult. — On the lifth day Ps. JtyacintJd showed an ai)undant, smooth, 

 wet-shining, bright-yellow growth the whole length of the slant, and a 

 copious yellow precipitate in the fluid. There was no liquefaction, or, 

 if any, only the merest trace on one side at the bottom of the slant. 

 In corresponding tubes of Ps. cam^estris and Ps. phciseoli there was a 

 distinct liquefaction the whole length of the streak. On the seventh 

 day there was a slight liquefaction under the streak. This was plainest 

 in the lowermost part, but was not one-twentieth as much as in the 

 corresponding tubes of Ps. cmnpestris and Ps. pliaseoli. On the 

 fifteenth day the precipitate continued to be brighter yellow, and 

 there was decidedly less liquefaction than in corresponding tubes of 

 the two organisms just mentioned. The serum of the long slant 

 preserved its normal shape and color very well, even in the air, only 

 the middle part and the sides just above the fluid being sunken in and 

 dissolved away. On a scale of 10, the ability of these three organisms 

 to liquefy this serum was marked 7, 5, and 2, Ps. jyhaseoll liquefj^ing it 

 most readil}' and ^s'. kyacinthi^ least readily. On the thirty-second 

 day the precipitate in the V was 15 mm. wide and 7 mm. deep, and 

 was still a trifle yellower than in corresponding tubes of Ps. camj^estris 

 and Ps. pJmseoli., but the liquefaction was decidedly less. The serum 

 under the fluid still preserved much of its original color and was not 

 liquefied, free access of air being apparently necessary, in case of each 

 of these three organisms, to the operation of the chemical changes 

 ending in liquefaction. About one-half as much fluid was now present 

 in this tube as in the corresponding tubes of Ps. cainpestris and Ps. 

 phaseoli. This fluid was strongly alkaline. 



On the same medium Ps. stevxtrti made an excellent bright buflf- 

 yellow growth, but there was no trace of liquefaction (32 days). 



Nutrient Gelatins. 



Ps. hyacintJd grew better on beef broth gelatins made strongly 

 alkaline to litmus (neutral to phenolphthalein) than on those which 

 received less caustic soda and were feebly acid or feebly alkaline to 

 litmus. It grew well, however, in beef broth gelatin first rendered 

 neutral to phenolphthalein and then feebly acidulated with malic acid. 

 A still better growth was o})tained ])y adding cane sugar to this acid 

 gelatin, the best growth of all })eing with +18 and +51 malic acid 

 gelatin with the addition of 5 or 10 per cent cane sugar. The compo- 

 sition of the throe gelatins on which the best growth was obtained is 

 given below: 



(1) Slock 205.—\,bm gr. finely minced lean beef; 8,000 c. c. distilled water. 

 Mixed and ])nt into a cool box for 24 lionrs. Tben in steamei- U hours at 70° to 90° 



