The Invasion of the Body by Bacteria 73 



have specific reactions, the cells of the respiratory centers 

 seeming to be most profoundly affected by them. 



The diphtheria bacillus, when observed in ordinary throat 

 infections, is seen to produce a pseudomembranous angina. 

 This results in part from the irritative local action of the 

 organism, which it shares in common with many others, and 

 in part from some coagulating product which it shares in 

 common with a few pneumococcus, streptococcus, etc. 

 Neither of these reactions is specific, but subsequent to these 

 early manifestations comes depressant action on the nervous 

 cells with palsy, peculiar to the products of the diphtheria 

 bacillus, and therefore specific. 



It is upon the peculiar specific reactions of the bacterio- 

 toxins that their ability to produce distinctive clinical con- 

 ditions depends, and that we are able to recognize them as 

 the essential factors in the production of any disease. 



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 activity 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. 



The mode by which this 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 

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



