91 



Sixteenth day. 



(1) C'/iec/:.— Growth decidedly yellow, still thin. ■ 



(2) Fruit sugar {one-half c. c. .sirup).— Growth has continued. It is wet-shining, very 

 smooth, and extremely copious. About 10 times as much growth as in the check 

 tube. Fructose distinctly favors growth unless all of this excess is attributable to 

 the sodium lactate formed by neutralizing the lactic acid, which is extremely improb- 



aV)le. 



(3) Frml sugar {1 c. c. sirup). — A marked increase of growth during the last 4 

 days. A considerable part of the slant which was then free is now covered. The 

 slime is i>ale yellow; the surface is very smooth and wet-shining. 



Thirtieth day. 



(1) Gieck. — Surface so dry that not ail of the colonies have fused. No crystals. 

 No stain of the agar. 



(2) Fruit sugar {one-half c. c. siru})).— The pale yellow, wet-shining, smooth slime 

 is 3 mm. deep over the whole surface of the slant. The color is dull yellow, but there 

 is no reason for thinking it contaminated. No brown stain. No crystals in the 

 agar. Growth has been enormously stimulated by this sugar. 



(3) Frintmgar [1 c c. sirup). — The entire surface of the slant (15 by 53 mm.) is 

 now covered with a pale yellow, smooth, very wet-shining slime. There is no brown 

 stain, and there are no crystals in the agar. 



SEVENTEEN PER CENT SUGARS. 



Mr. Dorsett's +15.5 sugar-free agar was also the basis of all of these tests. Each 

 tube contained exactly 10 c. c. of agar to which was added 2 grams of the sugar to be 

 tested. The slant surfaces were all inoculated in the same manner, and with approxi- 

 mately the same amount of material, viz, loops of bright-yellow slime from a coconut 

 culture 8 days old. 



First day (22 hours at 27° to 30° C). 



(1) Check. — A distinct, wide, pale yellow streak. 



(2) Grape sugar {2 gr. Merck's c. p. anhydrous). — Streak not visilile. 



(3) Qme sugar [2 gr. white commercial). — A meager growth. Gne-tenth to one- 

 twentieth as much as in the check tube. For the most part, tlie streak is mvisible 

 and nowhere shows more than a trace of growth. 



Fourth day (temp. 27° to 31°). 



(1) Clieck.— 'Streak smooth, wet-shining and rather bright yellow, but not dense 

 enough to be opaque. It is 72 by 5 to 6 mm. The margins of the streak are distinct 

 and there is no whitish efflorescence on the surface of the agar arcjund tlie streak. 



(2) drape su.g(tr.—Do\\hiiu\. No visible growth excei)t in very favorable lights. 

 If any growth at all, not one one-hundredth as much as in the check tube. There 

 can be no doubt that 17 per cent grape-sugar agar exerts a very distinct retarding 

 influence on I's. hyacinth i. 



(3) Cane sugar.— A well-developed streak 62 by 5 to 8 nun. It appears to beas dense 

 as in the check tube, but is paler yellow, i. e., the color is exactly that of a 4 days' 

 growth of I's. (■a)iipeslris on tlu^ check agar. This tube and the check tul)e are in 

 marked contrii,«t with the preceding. 



Eighth day. 



(1) Check. — The streak has thickened ;i little, but has not wid('ne<l. 



(2) drape sugar.— \\\vAt looked on the fourth day like mere drieil-out portions of 

 the slime used in making the inotuilation has now devehjped as a distinct growth in 



