INFECTION AND INTOXICATION. 65 



existence, but at times invade the tissues and produce 

 disease; and the purely parasitic forms that are unknown 

 except as we find them in diseased animals and in the 

 discharges from them. The preceding scheme, which 

 is a modification of that given by Kruse, 1 illustrates the 

 relationship of the different forms of bacteria to tissue 

 lesions. 



Just what result will follow the introduction of micro- 

 organisms into the tissues cannot always be accurately 

 prejudged, because of the numerous modifying conditions 

 that may arise. If the organisms belong to the purely 

 saprophytic bacteria, or if they are parasitic bacteria un- 

 able for some reason, such as will be described below, to 

 maintain themselves in the living animal, means are at 

 once adopted for getting rid of them, and certain defensive 

 tissue-reactions are observed. 



It is probable that the disposition of the micro-organ- 

 isms is similar to that of inert particles which, accord- 

 ing to the researches of Siebel, accumulate in the smaller 

 capillaries of the lung, liver, spleen, and bone-marrow, 

 and are slowly transferred to the surrounding tissues, 

 either to be collected in the connective tissues, carried 

 to the lymphatic nodes, or excreted with the bile, succus 

 entericus, sweat, or other excretion, discharged from the 

 surface of the mucous membranes, pulmonary alveoli, 

 tonsils, etc. The bacteria that are not so excreted are 

 probably slowly discharged in the lymphatic nodes and 

 bone-marrow. It is fairly certain that the bacteria, even 

 though they may not find the conditions of growth in 

 the body suitable for them, may, at least in the spore 

 stage, remain alive for a long time, Wyssokowitsch hav- 

 ing found that the spores of Bacillus subtilis may remain 

 alive in the spleen as long as three months. 



The pathogenic bacteria are in many cases similarly 

 disposed of, though they not infrequently appear in the 

 urine and milk, presumably from eliminative efforts on 

 the part of the kidneys and mammary glands. Whether 



1 Flugge's Die Mikro-organismen, i. p. 276. 

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