110 INFECTION. 



Infection of the genito-urinary tract and the reproductive 

 organs may occur through the circulation or by direct contact 

 with either pus cocci, the gonococcus, the tubercle bacillus, or 

 the virus of syphilis. 



Infection with the syphilis virus may take place through 

 the placenta. So too may that of typhoid, tuberculosis, 

 anthrax, and relapsing fever. Puerperal sapnemia is an infec- 

 tion of retained portions of the placenta or foetal membranes 

 by the streptococcus or colon bacillus (see also page 101). 

 Intra-uterine infection usually occurs through the placenta. 



The bladder and accessory organs may be infected from the 

 urethra, and the infection may spread from here to the ureters 

 and kidneys. Infection of the kidney may occur also from 

 the adjacent tissues and through the blood. 



The canal of the external ear contains many non-pathogenic 

 germs, especially the Micrococcus cereusflavus. They diminish 

 in number near the tympanum. 



All these germs gain lodgement in or on these various 

 sources of infection from the air, food, drink, the soil, the 

 bodies of dead animals, and the excreta of persons sick with 

 an infectious disease ; but before infection can occur it is 

 necessary that the bacteria enter the tissues themselves in 

 sufficient number, and that they multiply there, when the 

 natural resistance of the body is diminished. 



Blood-current : According to Kruse, bacteria gain entrance 

 to the blood-current by : 



1. Passive entrance through the stomata of the vessels 



where the pressure of the inflammatory exudate is 

 greater than the intravascular pressure. 



2. Entrance into a vessel in the bodies of leucocytes. 



3. Penetration of the vessel-wall by the growth of the 



organism. 



4. Entrance through the lymphatics either passively or 



within a leucocyte. 



Elimination of bacteria from the blood : It has been shown 

 that bacteria eventually accumulate in the finer capillaries, 

 especially those of the liver, spleen, lungs, and bone-marrow. 

 From the capillaries they are carried to the surrounding 

 tissues, and finally to the lymph-nodes ; or they are excreted 



