MICROCOCCI IN WATER. 405 



white colony appears surrounded by a sparkling crown. Upon 

 agar-agar the growth is peculiar, a stiff, wrinkled, readily 

 detached deposit forming. The hay-bacillus forms central 

 spores, which are somewhat thicker, but considerably shorter 

 than the mother-cells. It is found in the air, water, dust, 

 feces, hay, etc. In order to obtain the organism in pure culture 

 hay is. cut up into small pieces, which are covered with water in 

 an Erlenmeyer flask, and exposed to a boiling temperature for 

 fifteen minutes. In this way all of the germs are destroyed, 

 with the exception of the resistant spores of the hay-bacillus. 

 These then grow, and after two or three days they form a super- 

 ficial membrane upon the hay-infusion. 



23. Potato-bacillus (Bacillus Mesentericus). Three varieties 

 of this microorganism are distinguished : bacillus mesentericus 

 vulgatus, fuscus, and ruber. The last, especially, which im- 

 parts a rose tint to potatoes upon which it grows, possesses per- 

 manent forms of extraordinary resistance, which withstand 

 boiling for from five to six hours. In proportion to the cell the 

 spore is quite large. The cultural peculiarities of the organism 

 resemble those of the hay-bacillus. Upon potatoes the bacillus 

 gives rise to a wrinkled coating. Milk is coagulated and pep- 

 ton ized. 



24. Bacillus Spinosus. This is a strictly anaerobic, motile 

 rod. Its colonies in gelatin form iridescent globules, with thorn- 

 like processes. Gelatin is liquefied, with the formation of gas. 

 Stab-cultures, before liquefaction takes place, present the appear- 

 ance of a prickly caterpillar (Ltideritz). The bacillus spinosus 

 grows both at room-temperature and at the temperature of the 

 body. It forms central spores, the rod becoming at the same 

 time spindle-shaped (clostridium). The bacillus is usually 

 found in garden -earth. 



n. MICROCOCCL 



i. NOT LIQUEFYING GELATIN. 



(a) Chromogenic. 



25. Micrococcus Aurantiacus. This is a round or oval coccus, 

 arranged in groups. The cultures are yellow, slimy, knob- 

 shaped, and they do not extend greatly in width. 



26. Micrococcus Versicolor. This is a small coccus, arranged 

 in groups or in pairs. It occurs with extraordinary frequency 

 in the air. The colonies are irregular in shape, with a yellowish- 

 green color. They exhibit, especially upon gelatin, a mother- 

 of-pearl iridescence, and they cause fermentation in nutrient 

 media containing glucose. 



