150 CLINICAL BACTERIOLOGY. 



catheterization by way of the right carotid), it has been 

 possible to induce endocarditic changes of malignant char- 

 acter in experiments on animals by intravenous injection 

 of the exciting agents of inflammation and suppuration. 

 The same result may be attained without this serious pro- 

 cedure if the bacterial material is introduced into the vein 

 in the form of a suspension that contains coarse particles 

 for instance, from a potato-culture. The particles, with the 

 contained and adherent microorganisms, lodge upon the 

 valves, and thus form the starting-point of endocarditic 

 changes. 



Bacteriologic Diagnosis. In doubtful cases it is advis- 

 able to examine the blood bacteriologically (p. 162). As 

 has been mentioned, it is sometimes possible to demonstrate 

 the microorganisms in the circulating blood, and the diag- 

 nosis of ulcerative endocarditis is then justified. In the 

 majority of cases, however, examination of the blood yields 

 negative results, and even in such cases as exhibit a dis- 

 tinctly malignant character. The clinical diagnosis may, 

 therefore, receive but little support from bacteriologic ex- 

 amination in connection with this disease. 



PERICARDITIS. 



Also with regard to pericarditis, the distinction between 

 primary and secondary inflammation can not readily be 

 made from the etiologic standpoint. The principal factor 

 in the causation of pericarditis likewise is acute articular 

 rheumatism, whose exciting agent, as has been stated, is 

 unknown. Traumatic pericarditis is either to be referred 

 to the action of bacteria that gain entrance into the peri- 

 cardial cavity simultaneously with the inception of the 

 injury, or, in the case of nonpenetrating wounds of the 

 thorax, a point of lessened resistance is established in the 

 pericardium in consequence of rupture of blood-vessels, 

 ecchymosis, etc., resulting from the contusion of the chest, 

 in which microorganisms circulating in the blood lodge 

 and give rise to inflammation. Pericarditis in the sequence 

 of erysipelas is dependent upon the streptococcus pyogenes ; 

 the pericarditis attending pneumonia, upon the diplococcus 

 of Frankel ; puerperal and pyemic pericarditis, upon the ex- 

 citing agents of suppuration. 



A distinct position is occupied by tuberculous pericarditis , 



