The appearance produced by the growths in the test-tubes can be in most cases sufficiently examined with the naked eye (Fig. 261). In some cases the jelly is partially liquefied, while in others it remains solid. The growths may be abundant or scanty, coloured or colourless. When liquefaction slowly takes place in the needle tracts, the appearances which result are often very delicate and in some very characteristic. The appearance of a simple white thread with branching lateral filaments, of a cloudiness, or of a string of beads in the track of the needle, may be given as examples. In some cases much may be learnt by means of a magnifying-glass. Beneke recommends that gelatine culture tubes should be inoculated by making a puncture quite at the side of the medium, close to the glass. The advantage of this method over the plan of inoculating the mass in the middle is that the growing culture can be microscopically examined from the outside, and various details made out, such as the nature of the growth, the comparative appearance of colonies near the surface and those situated more deeply, and the presence of one or more distinct organisms. If the tubes used have the opposite sides flat and parallel, such examinations will be still further facilitated. _Plate Cultivations._--By this method a mixture of bacteria, whether in fluids, excreta, or in cultivations on solid media, can be so treated that the different species are isolated one from the other, and perfectly pure cultivations of each of the cultivable bacteria in the original mixture established in various nutrient media. We are enabled also to examine under a low power of the microscope the individual colonies of bacteria. The same process, with slight modification, is also employed in the examination of air, soil, and water. In order to spread out the liquid jelly evenly on the surface of a glass plate, and to hasten its solidification, it is necessary to place the plate upon a level and cool surface. The glass plates are sterilised in an iron box placed in the hot-air steriliser, at 150° C., from one to two hours. The damp chambers for the reception of the inoculated plates are prepared by cleansing and washing out with one in twenty carbolic acid the shallow glass dish and bell-cover (Fig. 253). A piece of filter-paper should cover the bottom of dish, moistened with the same solution.