METHODS AND CHANNELS OF INFECTION 679 



and in the various septicemias. They may pass through the epithelium 

 of the kidney and be eliminated in the urine; they may pass through the 

 liver and be eliminated in the bile, finally passing out through the in- 

 testines; and they may pass through the mucous membranes of the 

 intestine and possibly pass through the glandular epithelium of the 

 sebaceous and sweat glands and be eliminated through the skin. They 

 have also been known to pass through the glandular epithelium of the 

 milk glands when these glands are not grossly diseased and through the 

 salivary glands. It has been recently well demonstrated that there 

 must be some form of lesion in the liver and kidney in order for the 

 microorganisms to pass through. Infectious microorganisms are some- 

 times destroyed by the lysins in the blood, carried to and deposited 

 in the spleen and bone marrow and gradually disintegrated and 

 dissolved. 



In certain infections in which a recovery seems to have occurred 

 all the infectious microorganisms are not always eliminated from the 

 body. As mentioned previously, B. typhosus and Bact. diphtheria are 

 frequently carried by persons fully recovered from these diseases. 

 Sometimes, however, inflammatory infections are set up by these bac- 

 teria. It has been suggested on seemingly good evidence that inflam- 

 mations of the gall-bladder and gall-stone formation may be due to the 

 toxic action of the bacteria of typhoid fever which have been retained 

 in the gall-bladder for a considerable time following an attack of typhoid 

 fever. It is known that frequently repeated attacks of malaria are due 

 to the retention of some of these protozoan parasites for a time in the 

 quiescent stage. Repeated attacks of erysipelas caused by the Strept. 

 pyogenes may also be due to the same condition. It is also claimed by 

 some (Von Behring) that Bact. tuberculosis is taken into the body in 

 infancy, that it is not eliminated, and that it sets up infection in later 

 life. 



In conclusion should be mentioned one other indirect way in which 

 infectious agents are eliminated from the body, namely, by being 

 taken up by suctorial insects from the blood. It is necessary that this 

 be done in order to perpetuate the parasite and complete its life cycle in 

 certain instances, as with the mosquitoes in yellow fever and malaria. 

 In other instances the parasites are only taken up by the insect ana 

 subsequently injected into another individual or digested as the case 

 may be. This occurs with the ticks in the transmission of certain of 



