29 



also prove the absence of bacteria from healthy animals. 

 The familiar fact that a dead human foetus may remain in 

 the mother's body for months or years without putrefac- 

 tion, as in extra-uterine pregnancy, supports the same con- 

 clusion. Indeed, it has been repeatedly demonstrated 

 that certain bacterial species, even when injected in con- 

 siderable numbers directly into the blood or tissues of 

 the living animal, cannot be found after the lapse of 

 some hours ; they appear to suffer the same fate as un- 

 organized particles. Hiller even injected into his own 

 skin some bacteria obtained from putrid flesh, and ob- 

 served only a slight, transient, local oedema. 



This failure of putrefactive and other bacteria to re- 

 produce in healthy tissue seems to indicate their inability 

 to maintain the struggle for existence against the animal 

 cells indigenous to the soil. For seventy years a man 

 may eat, drink, and breathe the ordinary bacteria, and 

 carry a vast and varied assortment of them in his alimen- 

 tary canal, without suffering putrefaction ; yet so soon as . 

 his component cells are destroyed, generally, as in the X 

 death of the animal, or locally, as in the gangrene of a 

 toe, the tissues swarm with these minute organisms. 

 While some bacteria seem capable of development in 

 tissues only after the death of their competitors, the 

 animal cells, others exhibit this power in the presence 

 of these cells when the tide is turned against the latter 

 by the impairment of their nutrition, or by the presence 

 in the blood of material favoring the invaders. The 

 exudate on the cardiac valves frequently contains, not 

 only in ulcerous, but also in simple "rheumatic" endocar- 

 ditis, colonies of growing micrococci, a fact first observed 

 by Klebs and confirmed by Eberth, Ehrlich, and Osier. 

 In some cases it is demonstrable that the appearance 

 of the bacteria upon these vegetations was subsequent 

 to the inflammatory process. Abnormal blood compo- 

 sition seems to favor the development of some bacteria 

 which may gain access to the tissues. The presence of 

 glucose and increased metamorphosis of albuminous 

 blood-constituents in diabetes are usually considered 



