NUMBERS OF MICROORGANISMS 29 



conditions. No two soils, even from the same locality can be com- 

 pared on the basis of mere bacterial numbers without a detailed 

 knowledge of the physical and chemical condition of soil, treatment, 

 etc. In some soils, like very poor sandy soils, very acid peat soils 

 and abnormal acid or alkaline soils, the number of bacteria may be 

 much below 2,000,000 per gram. The sandy soils of the Pine- 

 barrens of New Jersey, for example, contain only 25,000 to 100,000 

 bacteria per gram, while certain acid peat and acid forest soils may be 

 nearly free from bacteria capable of developing on the common agar or 

 gelatin plate. Very heavily manured soils, such as greenhouse soils 

 or market garden soils, particularly at the time of active decomposition 

 of the organic matter, may contain over 200,000,000 bacteria per gram, 

 even as shown by the plate method. 



Bacterial numbers in manure. Manure consists of (1) solid excreta, 

 (2) straw, hay or peat litter, and (3) urine. Solid excreta are very rich 

 in bacteria. The bacterial numbers in feces were found 51 to be very 

 variable; 1 gram of fresh human feces may contain 18,000,000,000 

 bacteria. Dry cow manure was shown 52 to contain, by weight, 9 to 

 20 per cent bacteria. One gram of fresh cow manure (17.65 per cent 

 dry weight) should thus contain 18 to 40 billions bacteria, the larger 

 number of which consists of dead cells. However, by the plate method, 

 only 40 to 70 millions bacteria per gram of cattle manure and 100 to 150 

 millions per gram of horse manure were obtained. By the use of the 

 gravimetric method, Lissauer 53 estimated that 4.26 to 15.67 per cent of 

 the feces of man (on the average 9 per cent), 3.54 to 9.08 of dog, 0.41 

 to 1.31 of rabbit and 14.73 to 18.75 per cent of the feces of cattle con- 

 sisted of bacteria; the kind of food (vegetable or animal) influenced the 

 numbers. Since 1 mgm. of dry bacteria contains 4,000,000,000 cells, 

 1 mgm. of cow feces would contain 63 to 80 millions of bacteria. By the 

 plate method, manure of stall-fed cattle was found 54 to contain 1 to 120 

 million bacteria per gram, while that of cattle on pasture contained only 



61 Matzuschita, T. Untersuchungen liber die Mikroorganismen des men- 

 schlichen Kotes. Arch. Hyg. 41: 210-255. 1901. 



62 Stoklasa, J. tlber die Wirkung des Stallmistes. Ztschr. landw. Versuch. 

 Osterreich. 10: 440. 1907. 



63 Lissauer, M. Uber den Bakteriengehalt menschlicher und tierischer Faces. 

 Arch. Hyg. 58: 136-149. 1906. 



64 Gruber, Th. Die Bakterienflora von Runkelriiben, Steckruben, Karotten, 

 von Milch wahrend der Stallf iitterung und des Weideganges einschlieszlich der 

 in Streu, Gras und Kot vorkommenden Mikroorganismen und deren Mengen- 

 vehaltnisse in den 4 letzten Medien. Centrbl. Bakt. Abt. II, 22: 401-416. 1909. 



