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BACTERIOLOGY 65 We cannot as yet speak definitely with regard to the may not be detectable in the peripheral circulation during part played by enzymes in these toxic processes. Certain life. In another class of diseases, the organisms first enzymes as regards their con- produce some well-marked local lesion, from which secondEazymes. (toxins j^-ong resemble 0f precipitation and relative instability, ary extension takes place by the lymph or blood stream and the fact that in most cases a considerable period to other parts of the body, where corresponding lesions intervenes between the time of injection and the occurrence are formed. In this way secondary abscesses, secondary of symptoms has been adduced in support of the view that tubercle glanders and nodules, Ac., result; in typhoid fever enzymes are present. In the case of diphtheria Sidney there is secondary invasion of the mesenteric glands, and Martin obtained toxic albumoses in the spleen, which he clumps of bacilli are also found in internal organs, considered were due to the digestive action of an enzyme especially the spleen, though there may be little tissue formed by the bacillus in the membrane and absorbed change around them. In all such diseases there is seen into the circulation. According to this view, then, a part a selective character in the distribution of the lesions, at least of the directly toxic substance is produced in the some organs being in any disease much more liable to living body by enzymes present in the so-called toxin infection than others. In still another class of diseases obtained from the bacterial culture. Recent researches go the bacteria flourish in some particular part of the body, to show that enzymes play a greater part in fermentation and the symptoms are due to toxic absorption from it. by living ferments than was formerly supposed, and by Thus, in cholera the bacteria are practically confined to analogy it is likely that they are also concerned in the | the intestine, in diphtheria to the region of the false processes of disease. But this has not been proved, and membrane, in tetanus to some wound. In the lasthitherto no enzyme has been separated from a pathogenic mentioned disease even the local multiplication depends bacterium capable of forming, by digestive or other action, upon the presence of other , bacteria, as the tetanus the toxic bodies from proteids outside the body. bacillus has practically no power of multiplying in the The action of toxins is little understood. It consists healthy tissues when introduced alone. in all probability of disturbance, by means of the chemical The effects produced by bacteria may be considered affinities of the toxin, of the highly complicated molecules under the following heads : (1) tissue changes produced of living cells. This disturbance results in disintegration in the vicinity of the bacteria, either at the primary or to. a varying degree, and may produce changes visible on secondary foci; (2) tissue changes produced at a distance microscopic examination. In other cases such changes by absorption of their toxins; (3) symptoms. The cannot be detected, and the only evidence of their occurrence changes in the vicinity of bacteria are to be regarded may be the associated symptoms. The very important partly as the direct result of the action of work of Ehrlich on diphtheria toxin shows that in the toxins on living cells, and partly as indicating Tissue molecule of toxin there are at least two chief atom a reaction on the part of the tissues. (Many ^ groups—one, the “ haptophorous,” by which the toxin such , changes are usually grouped together under the molecule is attached to the cell protoplasm ; and the other heading of “inflammation” of varying degree—acute, the “ toxophorous,” which has a ferment-like action on the subacute, and chronic.) Degeneration and necrosis of living molecule, producing a disturbance which results in cells, hamiorrhages, serous and fibrinous exudations, the toxic symptoms. On this theory, susceptibility to a leucocyte emigration, proliferation of connective tissue and toxin will imply both a chemical affinity of certain tissues other cells, may be mentioned as some of the fundamental for the toxin molecule and also sensitiveness to its action. changes. Acute inflammation of various types, suppuraA bacterial infection when analysed is seen to be of the tion, granulation tissue formation, Ac., represent some of nature of an intoxication. There is, however, another all- the complex resulting processes. The changes produced Bacteriai “]1Portantt ie factor concerned, viz., the multiplica- at a distance by distribution of toxins may be very infectioa. .°^ ^ living organisms in the tissues; manifold—cloudy swelling and fatty degeneration, serous this is essential to, and regulates, the supply of effusions, capillary haemorrhages, various degenerations of toxins. It is important that these two essential factors muscle, hyaline degeneration of small blood-vessels, and, should be kept clearly in view, since the means of defence in certain chronic diseases, waxy degeneration, all of which against, any disease may depend either upon the power of may be widespread, are examples of the effects of toxins, neutralizing toxins or of killing the organisms producing rapid or slow in action. Again, in certain cases the them. It is to be noted that there is no fixed relation toxin has a special affinity for certain tissues. Thus in between toxin production and bacterial multiplication in diphtheria changes both in nerve cells and nerve fibres the body, some of the organisms most active as toxin have been found, and in tetanus minute alterations in the producers having comparatively little power of invading nucleus and protoplasm of nerve cells. the tissues. The lesions mentioned are in many instances necessarily We shall now consider how bacteria may behave when accompanied by functional disturbances or clinical sympthey have gained entrance to the body, what effects may toms, varying according to site, and to the Sym toms P The pro- ke Pr°duced, and what circumstances may modify nature and degree of the affection. In addition, duction of disease in any particular case. The extreme however, there occur in bacterial diseases symptoms to disease. instance of bacterial invasion is found in some of which the correlated structural changes have not yet been the septicaemias in the lower animals, e.y., anthrax demonstrated. Amongst these the most important is septicaemia in guinea-pigs, pneumococcus septicaemia in fever with increased proteid metabolism, attended with rabbits. In such diseases the bacteria, when introduced disturbances of the circulatory and respiratory systems. mto the subcutaneous tissue, rapidly gain entrance to the Nervous symptoms, somnolence, coma, spasms, convulsions, blood stream and multiply freely in it, and by means of and paralysis are of common occurrence. All such phenotheir toxins cause symptoms of general poisoning. A wide- mena, however, are likewise due to the disturbance spread toxic action is indicated by the lesions found—cloudy of the molecular constitution of living cells. Alteraswelling, which may be followed by fatty degeneration, in tions in metabolism are found to be associated with some internal organs, capillary haemorrhages, Ac. In septic- of these, but with others no corresponding physical change aemia in the human subject, often due to streptococci, can be demonstrated. The action of toxins on various the process is similar, but the organisms are found glands, producing diminished or increased functional especially in the capillaries of the internal organs and activity, has a close analogy to that of certain drugs. S. II. — 9