The Invasion of the Body by Bacteria 75 



THE INVASION OF THE BODY BY BACTERIA. 



Some bacteria whose invasiveness is insufficient to enable 

 them successfully to maintain life in healthy tissues, occa- 

 sionally get a foothold in diseased tissues and assist in morbid 

 changes. This is sometimes seen in what is described by 

 the surgeons as sapremia, in which various saprophytic 

 bacteria, possessing no invasive powers, by growing in the 

 putrefying tissues of a gangrenous part, give rise to poison- 

 ous substances which when absorbed by the adjacent 

 healthy tissues produce constitutional disturbances, such 

 as depression, fever, and the like. 



Bacteria with limited invasive powers and intracellular 

 toxins can at best occasion local inflammatory effects. 

 Such organisms not infrequently vary, however, and when 

 of unusual vitality may survive entrance into the blood and 

 lymph circulations and occasion bacteremia, or, as it is more 

 frequently called, septicemia, a morbid condition charac- 

 terized by the presence of bacteria in the circulating blood. 

 When bacteria entering into the circulation are unable to 

 pervade the entire organisms and continue in the circulation, 

 they may collect in the capillaries of the less resisting tissues, 

 producing local metastatic lesions, usually purulent in 

 character. This form of invasion results in what is surgically 

 known as pyemia. 



The mode by which the entrance of bacteria into the 

 circulation is effected differs in different cases. Kruse * 

 believes that they sometimes are passively forced through 

 the stomata of the vessels when the pressure of the inflam- 

 matory exudate is greater than that of the blood within 

 them; that they may sometimes enter in the bodies of 

 leukocytes that have incorporated them; that they may 

 actually grow through the capillary walls, or that they reach 

 the blood circulation indirectly by first following the course 

 of the lymphatics. 



Toxemia results from the absorption of the poisonous 

 bacterial products from non-invasive bacteria, as in tetanus. 



* Fliigge, "Die Mikroorganismen, " vol. i, p. 271. 



