Metastasis. 153 



the bacteria first multipl_\ing- at this point of invasion and then 

 either by way of the lymph passages, conveyed to the blood. 

 or directly growing through or actively penetrating the deli- 

 cate walls of the capillaries. Some bacteria are motile and are 

 able to actively progress because of this property, or because of 

 their minute size ma}- be passively conveyed through the lymph 

 spaces. Generally at the point of entrance the local action of the 

 bacteria causes a focus of destruction varying in type with the 

 form of bacteria present, as a suppurative liquefaction or ichorous 

 softening (furuncle, suppurative wounds of the skin) ; coincidently 

 the destruction of the walls of the capillaries and veins permits 

 the bacteria to gain access to the blood and circulate with it and 

 to be carried to the heart and lung or from the intestine to the 

 liver. Bacteria, too. because of their minute size may traverse 

 capillary areas and therefore often pass from the lesser to the 

 general circulation and become scattered widely throughout the 

 system. In a strict sense they should be regarded as emboli, al- 

 though primarily because of their minuteness they occasion no me- 

 chanical disturbances but remain suspended here and there in the 

 vascular tubes, as at places where the blood current is temporarily 

 hindered (a joint) or where there are inequalities in the intima 

 (valves, sharp bends in the capillaries, renal glomeruli). At such 

 sites they induce the same type of changes as at the point of en- 

 trance, causing inflammatory reaction, suppuration, etc., and multi- 

 plving at first to the production of a definite metastatic focus and 

 later making their mechanical obstructive eflfects appreciable when 

 thev have developed into masses and clumps. In other cases the bac- 

 teria may from the first be disseminated in the blood in small clumps. 

 or as is usually the case they may adhere to bits of thrombi which 

 have been broken loose. Under such circumstances mechanical 

 occlusion and specific action are to be expected coincidently or in 

 close succession. Precisely as in case of simple embolism a smaller 

 or larger infarction is produced and within the tissue of the 

 infarct, filled up with coagulated blood and necrosed, the bacteria 

 mav multiply to great numbers, transforming the infarct, accord- 

 ing to the specific properties of the bacteria of the embolus, into a 

 suppurating focus or breaking it down into an ichorous mass. 



The most common example of malignant embolism is met with 

 in umbilical phlebitis, frequently seen in newly born animals. In 

 case after section of the umbilical cord, dirt infected with bacteria 

 (from dung, pus, dust from the straw of the animal's bed, the 



