Page:The New International Encyclopædia 1st ed. v. 06.djvu/338

* DISEASE. 290 DISEASE. known as a pure culUire, i.e. a growth of this germ absolutely free from any other living sub- stance. It must be possible to induee the same or a similar disease in animals by injeetinjj them with this pure eullure. Comparatively few dis- eases as yet fullill all of these requirements. Among the most important of the diseases which have been proved to be of germ origin may be mentioned anthrax, actinomycosis. Asiatic chol- era, bubonic plague, acute cerebrospinal menin- gitis, diphtheria, erysipelas, glanders. gonorrha>a, inlluenai, leprosy, malaria, pneumonia, relapsing fever, tetanus, tuberculosis, and typhoid. Uf the more important of the diseases which from their beliavior are believed to be of germ origin, but in which the germs have not as yet been found, are hydrophobia, measles, scarlet fever, small{>ox, typhus, and whooping-cough. Bactehiologu AL 'J'ECiiNiguE. In many cases of disease a determination of the species of bacteria [ireseut may be made by means of a bacterial examination of pathological material during life. This is done in one of three ways: lirst, by cover-glass preparation: second, by culture; third, by animal inoculation. In some cases a little pathological material may be ob- tained on a sterilized platinum loop: in others a piece of absorbent cotton wound about a stiff wire and forming a "swab' is used, by means of which i)us or exudates inaj- be obtained and transported in a sterile test-tulje into which the swab is thrust; in still other cases fluid ma- terial may be obtained by aspiration. A cover- glass preparation is thus made: A very small amount of material is smeared over a cover-glass in such a way as to leave streaks of it and not a continuous layer. After being dried by being held in the fingers, charged side uppermost, over a iiunscn burner, it is passed rapidly three times directly through the Hame of the burner by means of a forceps, to 'fix' it. The cover- glass is then licld in the grasp of the forceps, charged side up and level, and the chosen stain- ing fluid is drojjped on it from a dropping bot- tle, till it is completely covered. The cover- glass is then heated over the flame and washed in water, and any other necessary processes are concluded, according to the method of staining employed. The cover-glass with the charged side down, and wet thoroughly with water, is placed on a microscopic slide, and the excess of water is removed by means of filter paper in the usual way. An oil-immersion lens is then used, for examination of the specimen. Culture mediums dilTer in difTerent cases. Potato, agar-agar, litmus-milk, glucose agar-agar, and glucose gelatin are used : but the best culture medium for general purposes is co- agnlatc<l blood serum. At the slaughter-house blood is obtained as it runs from the vessels of the beeves, preferably that which flows from the carol id artery, as it clots more quickly. The jar in which it is received is left in a cool place for twenty-four hours, .fter a few hours the clot is gently loosened from the sides of the jar. to facilitate its contraction, and after this the jar is not agitated. After about twenty-four hours the serum is removed with a pipette. Three parts of blood serum and one pari of glucose bouillon are mixed to form the culture medium, which is run into test ttihes in small quantities. The tubes are plared in a tilted position in the hot-air sterilizer and when withdrawn the -crum is found to be coagulated in a slanting position. .Material obtained on a 'swab,' e.g. from the throat of a suspected diplillicria patient, is light- ly smeared over the whole exposed surface of the blood serum in a culture-tube. The culture- tube is then placed in an incubator or thermo- stat, and the bacteria are allowed to grow on the nutrient surface, for subsequent examination with the microscope. Aninnil inoculations are made as follows: A small |>ieec of suspected material may be in- serted under the skin of a mouse by means of a platinum wire, or a little lluid may be injected un<ler the skin of a guinea-]iig or rabbit. After tlie death of the animal an autopsy is made, and various organs and tissues are examined micro- scopically. Special Kxami.xatioxs. In examining spu- tum for tubercle bacilli, a cover-glass |)rcpara- tion is made from a dense grayish-white |)article taken from the morning sputum. The tubercle bacillus is a slender rod varying from l.o micro- millimeters to 4 micromillimeters in length, and about 0.4 niicroniillimeler in breadth, generally slightly curved. The bacilli occur singly, though in cultures they are sometimes found in chains of four to six links. Club-like forms and branches have been seen also. It must l>e dif- ferentiated from the smegma bacillus, Lust- garten's bacillus of svjjhilis, and certain others. sprrrM costainim; TriiKitn.F nAnLLre (x 1000). In examining for the bacillus of diphtheria, a blood-serum culture-tube is inoculated by means of a 'swab' with exudate from the tonsils of the patient, and is placed in the incubator for about fifteen hours. The resilting growth is examined by means of a stained cover-glass preparation. Mounted on a slide, the s|)ecimen is examined with a high-power lens. The bacilli will he found to be of vnrving size, from 1 to fi niicro- inillimeters long and 0..t to 1 micrmnillinieter broad, straight or slightly curved, with roimded ends, singly or in pairs. The ends may lie en- larged. Irregular forms are conunon. Clusters or bimdles and rnrel.v liranching fonns are found. For the detection of the plasmoilium of nialnrin, a fresh specimen of blood is taken from the lobule of the ear. and received on a cover-glass. This is inverted on a slide so as to spread the speci- men evenly, and nil superfluous blood is removed. Fixation may be secured by heating, or by im-