*Pigeon-Dung Bate as used for Hides.*--The bacteria contained in the intestines of birds and in bird dung have not been studied to the same extent as those of mammals, so that it is not possible to give anything but a meagre account of them. A microscopical examination of fresh pigeon dung, collected on a sterile Petri dish, showed debris of food, cellulose, etc., among the debris, a large number of dumb-bell bacteria (_b_) (Fig. 20), and a few motile pairs (_c_); no bacilli were seen. Cells of a saccharomyces (_a_) were also observed. From this pigeon dung attenuations were made by a modification of Soyka’s method,[82] and from the fourth attenuation a plate culture was made in ordinary nutrient gelatin. The colonies from this plate were principally of two varieties (both non-liquefying organisms), corresponding to the bacteria observed in the original dung. Large cultures were made in a Carlsberg vessel, as described in Chapter VI., and the effect of these cultures tried upon skin. No particular reducing effect was obtained. [82] The modification of Soyka’s method of making attenuations of bacteria is that of Günther (Bakteriologie, 1898, p. 204), and is carried out as follows:--On the inner surface of the cover of a sterile Petri dish (which is to be used for making the plate culture), place four drops of sterile broth, or sterile water; inoculate the first drop, by means of a platinum needle, with the material to be examined; heat the needle in the flame, dip it into the first drop, and, with the liquid adhering, inoculate the second drop. Proceed in this way, each time heating the needle, to the fourth drop. From this fourth drop a tube of nutrient gelatin is inoculated, and poured on to the plate. The cover is then put on, and the plate put into the incubator. The drops on the cover do not in any way contaminate the culture. [Illustration: Fig. 20.--Organisms in Pigeon Dung. × 1000.] A microscopical examination of a bating pit used for kips, showed an extraordinary mixture of bacteria, bacilli, vibrios, and monads; some comparatively large dumb-bell shaped bacteria, very motile, were present. The difference between the bating liquor and the fresh dung was very marked, especially in the variety of species present. Cultures made from several colonies isolated from the above bate, in a nutrient liquid, consisting of 10 litres water, and 20 grm. gelatin, peptonized by heating under pressure with 10 c.c. sulphuric acid, afterwards neutralizing with ammonia, and adding the soluble matter from 200 grm. bone-meal, had no action on skin. It would be unsafe to say from these two experiments that the bacterial effect of the pigeon-dung bate is negligible, but we may assume that it is different and not so great as with the dog-dung bate or puer. A complete research as to the various species of bacteria developing in the bird-dung bate is necessary before this question can be answered.