692 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



also mucus covers the surfaces. However, if the functional activity 

 of the small intestines is disturbed, bacteria may enter the lymphatic 

 structures (Peyer's patches, solitary follicles) low down in the small 

 intestines and produce infection. Such is the case with B. typhosus 

 of typhoid fever and with the Msp. comma of Asiatic cholera. 

 Bacteria which have been prevented from development in the small 

 intestines frequently find the opportunity in the large intestine. 

 Here the concentration of the various digestive juices is lowered and 

 the requisite condition for maximum bacterial growth is provided. 

 Nevertheless, infections of the large intestine with bacteria are not 

 common but may occur, colitis of various forms resulting. The 

 various dysentery amoebae very frequently develop in the large 

 intestine. 



The Genito-urinary Tract. The mucous membranes of the genito- 

 urinary tract, varying in male and female, present the same features 

 as those of other mucous membranes. Besides the secretion of mucus, 

 various other acid-containing secretions are often present. In addi- 

 tion, in the urinary tract the mechanical factor of irrigation removes the 

 microorganisms. Not infrequently, however, microorganisms do 

 enter these mucous membranes and produce serious infections, such 

 as the Treponema pallidum of syphilis, the M. gonorrhoea and the 

 B. chancroids mollis. Sometimes these membranes are infected with 

 ordinary pyogenic bacteria. 



The Conjunctiva. The conjunctiva is protected against infection 

 in several ways. First, the eyebrows with their hairs and the eye- 

 lashes prevent microorganisms and particles of dust and dirt carry- 

 ing microorganisms from entering the eye. Again, the lacrymal 

 secretion or the tears flowing across the eye from the outside in serve 

 to wash this membrane. Bacteria are frequently washed off the 

 conjunctiva and pass down through the lacrymal duct into the nose 

 where they meet the obstructions which have been previously dis- 

 cussed. In all probability the tears are only slightly antiseptic and 

 not germicidal at all. The conjunctiva is sometimes infected with 

 microorganisms and furthermore serves as a point of entrance into the 

 body when it itself is not infected. There is no doubt that the Bact. 

 influenza, the Strept. pneumonia, and other microorganisms may enter 

 the body and get into the lymphatic and blood circulation in this 

 way. 



