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forms a fluorescent pigment and a non-fluorescent-blue to blue-black 

 pigment. The blue character of the latter is best shown in an acid 

 medium; it is black when the reaction is neutral, brown when 

 the reaction is alkaline. A rose-red color frequently precedes the 

 blue pigmentation. The blue discoloration appears in milk only 

 when it is acid, and is for this reason best produced after some 

 development of lactic-acid bacteria. The bacillus is absolutely 

 non-pathogenic. 



Micrococcus Tetragenus. This organism is named from the fact 

 that it is generally found in tetrads, i. e., groups of four. The indi- 

 vidual cocci are about 1 micron in diameter. The organism is fre- 

 quently found in sputum and discharges from the nose. Under these 

 conditions it possesses a gelatinous envelope which generally surrounds 

 the group of four. In cultures the cocci are seen singly, ill pairs and 

 as tetrads. The coccus stains easily with the watery anil in solutions 

 and keeps Gram's stain. On gelatin the organism first forms small, 

 whitish points which later develop into thick, elevated, moist drops 

 of 1 to 2 mm. in diameter. They become confluent and finally form 

 a continuous moist growth. Gelatin and blood serum are not liquefied. 

 On agar the growth is not as abundant as on gelatin, but on potatoes 

 it is very luxuriant. The organism is pathogenic to white mice. If 

 small doses are injected these animals become somnolent and quiet 

 after two days, and they die three to six days after the injection. 

 The Micrococcus tetragenus is then found in large numbers in the 

 internal organs of the dead mice. Gray house mice are immune; 

 guinea-pigs develop local abscesses or a general septicemia. Intra- 

 peritoneal injection leafls to a purulent peritonitis. Larger animals, 

 such as rabbits, dogs, etc., are not susceptible. 



Micrococcus Agilis. This organism was first isolated from drinking 

 water. It is one of the few cocci which possess a flagellum, in con- 

 sequence of which they are motile. The coccus has a diameter of 

 about 1 micron; it grows on the ordinary media at room temperature 

 and forms a rose-red pigment. Gelatin becomes liquefied. The 

 organism forms pairs, tetrads, or short chains. Its motility can best 

 be exhibited in media containing 5 per cent, lactose. It can be 

 demonstrated that every coccus possesses one flagellum. When several 

 cocci adhere, particularly in tetrad form, the group generally performs 

 a kind of rotary motion around its own axis. Loeffler and Menge have 

 described a motile coccus forming a yellow pigment under the name 

 of Micrococcus agilis citreus. 



Sarcinae. All sarcinae are cocci which in multiplication arrange 

 themselves in square groups or packages which have been likened 

 to a bale of cotton. Sarcina lutea is composed of comparatively large 

 cocci about 1 micron or more in diameter. The sarcina form cannot 

 be as readily seen in stained specimens as in the hanging drop. The 

 growth of the organism on gelatin is at first slow and leads to the 

 formation of point-like colonies which later become larger and 



