The following bacteria have up to the present been isolated from dung (mostly dog dung), and studied in pure cultures:—

 1.Micrococcus ureae (Cohn). (Pasteur.)
 2.   "   fulvus (Cohn).
 3.   "   prodigiosus.
 4.   "   ureae liquefaciens.
 5.Bacterium sulphureum.
 6.   "   coli commune. (Fig. [15].)
 7.   "   coli anindolicum.
 8.Bacterium coli anaerogenes.
 9.   "   furfuris α (Wood). (Fig. [30].)
10.   "   furfuris β (Wood). (Fig. [31].)
11.Bacillus fluorescens putridus.
12.  "    "    "  liquefaciens.
13.  "  subtilis.
14.  "  saprogenes (Herfeld), three varieties.
15.  "  butyricus (Hueppe). (Fig. [23].)
16.  "  putrificus. (Fig. [19].)
17.  "  pyocyaneus.
18.  "  janthinus.
19.  "  coprogenes fœtidus.
20.  "  pyogenes fœtidus (a variety of B. coli).
21.  "  zenkeri.
22.  "  magnus.
23.  "  spinosus.
24.  "  liquefaciens (Eisenberg, Frankland).
25.  "  amylobacter (Van Tieghem).
26.  "  acidi paralactici.
27.  "  I.Isolated from horse manure by Severin, Centr. Bl. f. Bakt. (2), i., 97.
28.  "  II.
29.  "  III.
30.  "  from horse dung (anaerobic) Severin, Centr. Bl. f. Bakt. (2) iii., 708.
31.  "  from horse dung (anaerobic), No. 3, ditto.
32.  "  oedematis maligni (Vibrion Septique, Pasteur).
33.  "  mesentericus vulgatus.
34.  "  lactis aerogenes.
35.  "  cavicida (Brieger).
36.  "  albuminis (Bienstock).
37.  "  Bienstockii.
38.  "  tenuis.
39.  "  enteritidis sporogenes (Klein).
40.  "  lactis acidi (Ankerschmid, 1905).
41.  "  megatherium.
42.  "  cadaveris sporogenes (Klein) said to be identical with No. 16.
43.  "  thermophilus. (Houston).
44.  "  a. from puer. See p. 162.
45.  "  b. "  "    "
47.Bacillus mycoides.
48–61.14 species isolated from dog and pigeon dung by Prof. H. Becker. Zeit. f. Offentlich. Chemie. Heft xxiii. Jahrgang X. p. 447, includes B. erodiens (Fig. [16]).
62.Sarcina fimentaria (Lehmann and Neumann).
63.Streptococcus from sewage. (Houston.)
64.   "    brevis.
65.   "    longus.
66.   "    pyogenes.
67.   "    liquefaciens coli. (Gamgee Phys. Chem. 2.)
68.Streptothrix from stable manure. (Severin, 6.)
69.Spirillum serpens (Kutscher).
70.   "  tenue   "
71.   "  undula   "
72.   "  volutans  "  (Figs. [24] and 25).
73.   "  from pig dung. Smith, Centr. Bl. f. Bakt. 16, (1), 124
74–76.Vibrio, three species isolated by Kutscher.
77.Clostridium butyricum (Prazmowski), said to be identical with No. 25.
78.Streptococcus faecalis. Sidney Martin, 37 and 38; Ann. 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. Na2CO3 or 12 c.c. N/1 soda per litre. The amount of alkali may be increased to 0·15 per cent. Na2CO3 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.

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.

With the object of ascertaining the effect of the various species of bacteria contained in the dung upon skins, a large number have been isolated, and the effect of pure cultures in different media has been tried upon skin.[77] A number of the results have been published in the Journal of the Society of Chemical Industry. Professor H. Becker, who has done a great deal of this part of the work, is of opinion that the principal organisms concerned in the bating exist in the dog’s intestines, and belong to the group of coli bacteria. These are very widely distributed bacteria, and are found in the large intestines of mammals, and, as a consequence, in almost all soils, and in the mud of rivers and lakes. The principal variety is B. coli commune.