670 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



as those of tetanus, malignant edema, symptomatic anthrax and 

 emphysematous gangrene. 



The mucous membranes of the nose, throat and mouth are quite 

 resistant to infection. The epithelial coat, the mechanical action of the 

 mucus and saliva and possibly the slight bactericidal action of the 

 saliva are the barriers. Infections of the thin non-resistant mucous 

 membranes of the new-born do occur and necrosis sometimes results 

 (noma). The mucous membrane of the mouth and throat is frequently 

 the seat of primary infection when it is injured. The actinomycotic 

 fungus usually enters a lesion in the mucous membrane made by straws 

 and other substances. The ducts of the salivary glands also serve as 

 points of entrance for certain infectious agents. The tonsils are very 

 commonly the seat of infections especially with the Strept. pyogenes 

 and Strept. pneumonia. Septicemias, as for example those occurring 

 in diphtheria, and especially in scarlet fever, frequently arise from infec- 

 tion of the tonsils with Strept. pyogenes. These structures are also the 

 primary point of invasion in cases of acute rheumatism and possibly in 

 certain cases of pulmonary tuberculosis. The nasal mucous membrane 

 is undoubtedly more permeable to infectious agents than that of the 

 oral cavity. The microorganisms of acute epidemic meningitis, acute 

 poliomyelitis, measles, leprosy and glanders undoubtedly most fre- 

 quently enter the body through lesions in the membranes of the nose. 

 Infection may be carried into the nose directly or pass from the 

 conjunctiva through the naso-lachrymal duct. 



The flora found in the eye is quite extensive. The conjunctiva is 

 frequently the seat of primary infections. The pyogenic cocci and 

 the M. gonorrhoea are among the common infecting agents. It is 

 possible that certain points of infection are provided by the conjunctiva 

 being injured' by dust particles. The tears are not bactericidal and 

 only serve to mechanically wash the eye. Infections of the con- 

 junctiva are frequently very severe. There is no doubt also that other 

 pathogens are caught in the eye and washed into the nose where they 

 set up infections or are carried through the membranes to set up infec- 

 tion elsewhere. M. intracellularis var. meningitidis of epidemic menin- 

 gitis is known to pass in this way and possibly Bact. pestis of the plague 

 in certain instances. 



Infectious microorganisms after being taken into the body through 

 the nose or the mouth may either pass to the lungs through the trachea 



