or organisms isolated may be summarised under the following headings: Tissue changes:1 1. Local-i. e., produced in the neighbourhood of the bacteria. Position: (a) At primary lesion. (b) At secondary foci. Character: (a) Vascular changes and tissue reactions. (b) Degeneration Acute or and chronic. necrosis. 2. General (i. e., produced at a distance from the Symptoms: (a) Associated with known tissue changes. Permanent Preparations-Museum Specimens.— I. Tube Cultivations of Bacteria.-When showing typical appearances these may be preserved, if not permanently, at least for many years, as museum specimens, by the following method: 1. Take a large glass jar 25 cm. high by 18 cm. diameter, with a firm base and a broad flange, carefully ground, around the mouth. The jar must be fitted with a disc of plate glass ground on one side, to serve as a lid. 2. Smear a layer of resin ointment (B. P.) on the flange around the mouth of the jar. 3. Cover the bottom of the jar with a layer of cottonwool and saturate it with formalin. 4. Remove the cotton-wool plug from the culture tubes and place them, mouth upwards, inside the jar. (If water of condensation is present in any of the culture tubes, it should be removed by means of a 1 This table is adapted from Muir and Ritchie's "Bacteriology." capillary pipette before placing the tubes in the formalin chamber.) 5. Adjust the glass disc, ground side downwards, over the mouth of the jar and secure it by pressing it firmly down into the ointment, with a rotary move ment. 6. Remove the tubes from the formalin chamber after the lapse of a week, and dry the exterior of each. Fig. 157.-Bulloch's tubes. 7. Seal the open mouth of each tube in the blowpipe flame and label. If the cultivations are intended for museum purposes when they are first planted, it is more convenient to employ Bulloch's tubes. These are slightly longer than the ordinary tubes, and are provided with a constriction some 2 cm. below the mouth (Fig. 157)—a feature which renders sealing in the blowpipe flame an easy matter. II. Tissues.-The naked-eye appearances of morbid tissues may be preserved by the following method: 1. Remove the tissue or organ from the cadaver, using great care to avoid distortion or injury. 2. Place it in a wide-mouthed stoppered jar, large enough to hold it conveniently, resting on a pad of cotton-wool, and arrange it in the position it is intended to occupy (but if it is intended to show a section of the tissue or organ, do not incise it yet). 3. Cover with the Kaiserling solution, and stopper the jar. Kaiserling solution is prepared as follows: 4. After immersion in the formalin solution for twenty-four to forty-eight hours (according to size), transfer the tissue to a bath of methylated spirit for ten minutes. 5. Remove to a fresh bath of spirit and watch carefully. Immediately the natural colours show in their original tints, transfer to the mounting solution. The mounting solution consists of 6. After twenty-four hours in this solution transfer to a museum jar, fill with fresh mounting solution, and seal. 6a. Or transfer to museum jar and fill with liquefied gelatine, to which has been added 1 per cent. formalin. Cover the jar and allow the gelatine to set. When solid, seal the jar in the usual manner. XVII. OUTLINES FOR THE STUDY OF THE PATHOGENIC BACTERIA. (THE Outlines here given for the study of the pathogenic bacteria are those in use in the author's elementary classes for medical and dental students, and for those qualifying for the Public Health Service. They represent the minimum of individual practical work necessary for the acquisition of a sound knowledge of the more important specific organisms of disease. At the same time, it cannot be too strongly urged that every student should, if possible, work out each organism completely and thoroughly on the lines suggested in the Scheme for Study, on page 205.) The student who has conscientiously worked out the methods, etc., previously dealt with is in a position to make accurate observations and to write precise descriptions of the results of such observations. He is, therefore, now entrusted with pure cultivations of the various pathogenic bacteria, in order that he may study the life-history of each and record the results of his own observations-to be subsequently corrected or amplified by the demonstrator. In this way he is rendered independent of text-book descriptions, the statements in which he is otherwise too liable to take for granted, without personally attempting to verify their accuracy. For this reason none of the bacteria referred to in the following pages is described in detail, nor are any photomicrographic reproductions inserted. During the course of this work attention is also directed, as occasion arises, to such other bacteria, pathogenic or saprophytic, as are allied to the par ticular organisms under observation, or so resemble them as to be possible sources of error, by working them through on parallel lines. By this means a fund of information is obtained with regard to the resemblances and differences, morphological and cultural, of a large number of bacteria. The Organisms of Suppuration.-Whilst nearly all the pathogenic bacteria possess the power, under certain conditions, of initiating purely pyogenic processes in place of or in addition to their specific lesions (e. g., the Bacillus tuberculosis, the pneumococcus, etc.), there are a certain few organisms which commonly express their pathogenicity in the formation of pus. These are usually grouped together under the title of "pyogenic bacteria," as distinct from those which only occasionally exercise a pyogenic rôle. The organisms included under this heading are: 1. Staphylococcus pyogenes albus. 2. Staphylococcus pyogenes aureus. |