INFLAMMATION. 



113 



FIG. 40. BACTERIAL EMBOLUS IN THE LIVER. 



The bacteria have grown in a mass within the small 

 blood-vessel. The liver cells in the vicinity appear un- 

 changed. 



which leucocytes furnish (see p. 116), or may be carried off by the wan- 

 dering leucocytes; or, as is not infrequently the case, the decomposed 

 blood pigment may remain for some time, in situ, as the only mark of 



an earlier active inflammatory 

 process. 



Thus in the living animal ' 

 we can learn by direct obser- 

 '*>;/;', *. ""v.** ".*" .,**'' . >,'v' vat ion the way in which serum, 

 "* * " +' * *- ' -1 -:'"' '"'* '?' -'^/ V !*i*' - fibrin, and red and white blood 



cells get into the tissues and 

 upon free surfaces in certain 

 forms of injury involving the 

 blood-vessels. These materials 

 gathering in or upon the tis- 

 sues under these conditions are 

 called exudates, and this phase 

 of inflammation is commonly 

 called exudative inflammation. 



Let us now look at the 

 effect upon a living vascular 

 tissues of injury inflicted in 

 a different way. 



Injury from Micro-organisms. Suppose we inject into the ear vein of a 

 rabbit a small amount of a pure culture of a well-known and very com- 

 mon nicro - organism, Strepto- 

 coccus pyogenes. Little masses ..''"."."'*.*.' '". '''"*!. * 

 of the living germ will enter . .' i. *>:.*' .';'.'"**. 

 the heart and be driven out *.*,'.''" '.' '''; 



again through the arteries in ," -' ',* ''.,. '. ; '-*.' 



whose smaller twiglets or in * * .' -'..* 



the capillaries some of them 

 will lodge. Here in the living 

 tissues the bacteria may find 

 good nutrient conditions and 

 begin to proliferate, increasing 

 so rapidly in number that they 

 may distend the vessels in 

 which they lie. If after twenty- 

 four hours the animal be killed, 

 and one examine the organs in 

 which the bacterial emboli have 

 caught and grown in the liver, 

 for example he finds small 

 blood-vessels here and there distended with bacteria. But the paren- 

 chyma and interstitial tissue about them appear to be intact (Fig. 40) . 



1 Thoma has shown by similar studies on warm-blooded animals that the reaction 

 to injury is iu them essentially similar to that in the frog. 





FIG. 41. BACTERIAL EMBOLUS IN THE LITER WITH 

 NECROSIS. 



The bacteria are still largely confined to the vessel but 

 a few are outside. There is a zone of necrotic liver cells 

 about the growing mass of cocci. 



