290 WATER HYGIENE 
IX. All bacteria conforming to specified characteristics of VIII, except 
that fermentation of carbohydrates takes place without 
formation of gas. 
X. All bacteria conforming to group VIII except that no fermenta- 
tion of carbohydrates occurs. 
XI. All non-fluorescent, non-chromogenic, non-liquefying bacteria 
which ferment carbohydrates with the production of gas. 
XII. All bacteria conforming to specified characteristics of XI except 
that carbohydrates are fermented without gas. 
XIII. All bacteria conforming to specified characteristics of group XI 
except that no fermentation of carbohydrates occurs. 
Jordan (1901) studies 543 strains from the Illinois, Mississippi and 
Missouri rivers and developed the following classification: 
I. B. coli communis. 
II. B. lactis aerogenes. 
III. B. porteus. 
IV. B. enteritidis. 
V. B. fluorescens liquefaciens. 
VI. B. fluorescens non-liquefaciens. 
VII. B. subialis. 
VIII. Non-gas formers, non-fluorescent, non-spore forming bacilli 
which liquefy gelatin and acidify milk. 
IX. Similar to group VIII save that milk is rendered alkaline. 
X. Similar to group VIII save that gelatin is liquefied. 
XI. Similar to group IX, save that gelatin is not liquefied. 
XII. Similar to group XI, save that the reaction of milk is not altered. 
XIII. Chromogenic bacteria not included above. 
XIV. Chromogenic staphylococci. 
XV. Non-chromogenic staphylococci. 
XVI. Sarcine. 
XVII. Streptococci. 
The Bacterial Count. In early sanitary history, this was supposed 
to be a reliable index of pollution. Many standards were proposed in 
which it was stated that a water should not contain over a certain num- 
ber of bacteria per cubic centimeter to be regarded a good drinking 
water. One of the most elaborate of these was proposed by Miquel 
(1891). 
Less than 10 cells per cubic centimeter.............. excessively pure 
10-100 cells per cubic centimeter................... very pure 
