Rep. Loc. Gov. Board, 1907–9; Nature, March 3, 1910, p. 22. 79. _Bacillus bifidus._ 80. " _perfringens._ 81. " _bifermentans._ 82. " _funduliformis_ (Veillon). 83. " _capillosus._ 84. " _sporogenes._ 85. " _ventriosus._ 86. " _rodella III._ 87. _Staphylococcus parvulus._ 88. _Diplococcus orbiculus._ 89. _Coccobacillus preacutus._ 90. _Coccobacillus oviformis._ 91. _Bacillus faecalis alkaligenes_ (Petruschky). (79–90 are anaerobic bacteria, described and figured by Jungano and Distaso.) It will be surmised from the above list, to which additions are still being made, that the flora of the intestines is pretty extensive, and, consequently, the study of the part played by the various species of bacteria is a long and difficult one. The methods of isolating these bacteria, and the compositions of the media employed, would demand a treatise on bacteriology; but, for general purposes, a good liquid medium for the cultivation of puer bacteria is a gelatin peptone broth, made by digesting 10 grm. gelatin with 6-1/2 grm. 80 per cent. lactic acid in 100 c.c. water under pressure for three hours, neutralizing with ammonia, adding 1 grm. potassium phosphate, making up to 1000 c.c., and filtering. A sterile infusion of fresh dung may be used, but it is troublesome to prepare and not easy to get uniform in strength or composition. The culture liquids are left slightly alkaline, an alkalinity equal to 0·0636 per cent. Na_{2}CO_{3} or 12 c.c. N/1 soda per litre. The amount of alkali may be increased to 0·15 per cent. Na_{2}CO_{3} without affecting the growth of the bacteria. Of solid media, 10 per cent. nutrient gelatin, or in summer 15 per cent., is good if used at temperatures below 25° C. For higher temperatures, up to 39° and 40°, nutrient agar is required. The best nutrient gelatin for general work is made according to Klein’s formula.[76] For media in general, a most useful compendium is Abel’s Taschenbuch. [76] Klein, E., Micro-organisms and Disease (Macmillan), p. 22. See also, Kanthack and Drysdale, Practical Bacteriology (Macmillan 1896), p. 86. The number of bacteria in fresh fæces varies greatly, but is of the order of 10,000,000 per grm. of dry matter, capable of developing in nutrient gelatin. Of this number, about 100,000 are spore-bearing organisms. This estimate applies to healthy animals; in a diseased condition, the numbers vary enormously. Dr. A. C. Houston found in raw London sewage from 3,000,000 to 9,000,000 microbes per c.c., of which more than one-tenth were gelatin-liquefying organisms. There were only about 300 spores of aerobic bacteria, about 100,000 B. coli, 100 B. enteritidis sporogenes, and streptococci, in one gram of fæces.