250 IMPORTANT VARIETIES OF FISSION-FUNGI. 



colon bacterium. When ingested in meat, they make 

 men sick. Similar observations have been communicated 

 by Gaffky and Paak regarding meat (sausage), and by 

 Gaffky regarding milk. 



Also heated cultures are injurious. Repeated, subcu- 

 taneous injections of small quantities, according to 

 Sanarelli, produce an immunity against virulent Bact. 

 coli cultures (not against typhoid). Introduced into the 

 stomach, boiled cultures are less injurious. The gastro- 

 intestinal canal soon becomes accustomed to large quanti- 

 ties of poison, without the occurrence, on this account, of 

 an immunity against the subcutaneous injection of devital- 

 ized or living cultures (A. P., 1894, 353). 



Special Methods of Demonstration and Culture. — 

 If coli bacteria are abundantly present (stools), the agar 

 plate at 37° is employed for their isolation. After twenty- 

 four hours shake cultures in liquefied 2% grape-sugar agar 

 are prepared from numerous colonies. After sixteen to 

 twenty-four hours all colon bacteria present abundant gas 

 production, which leads to a breaking up of the nutrient 

 medium. (Fig. 11, p. 89.) The varieties which cause 

 fermentation of grape-sugar agar are examined micro- 

 scopically (to determine whether they are short rods 

 without spores, and whether they are motile) and are 

 transferred to lactose agar, milk, potato, ordinary and 

 grape-sugar bouillon, and peptone water (indol). If few 

 coli bacteria are present (water), then the water concerned 

 has 2 °lo grape-sugar and 1 % peptone added and is allowed 

 to stand for twenty-four hours in the incubator, and then 

 plates are prepared. It has also been recommended to add 

 to preliminary cultures 1% to 2% carbolic acid, 0.75% 

 anhydrous soda, and 1% hydrochloric acid, but we have 

 found no advantage from it. 



Forms of the Bact. coli described under separate 

 names. 



In the scheme for the peritrichous Bact. coli, as we have just 

 described and represented it, there are included very many subvarie- 

 ties, described as separate species. x 



1 Some investigators — for example, von Stocklin — undertake to 

 characterize separate forms of coli in relation to the number, length, 





