408 Chapter XIII 



the animal organism in getting rid of these micro-organisms becomes 

 more complicated than in the case of the defence made by the skin 

 The first of the mucous membranes to be exposed to contamination 

 by micro-organisms is the conjunctiva of the eye. At the moment 

 of birth it is in contact with the vaginal mucous membrane and 

 acquires from it some of its micro-organisms, both innocuous and 

 pathogenic. Tears fulfil the function of averting the danger resulting 

 [428] from this proximity and from the presence of micro-organisms in the 

 conjunctival sac in general. Ophthalmologists have shown that these 

 tears transport the organisms into the nasal cavity by means of the 

 lachrymal canal. To determine this point Bach 1 introduced a number 

 of Kiel water bacilli along with pyogenic staphylococci into the con- 

 junctival sac of various individuals. Seedings made with the tears 

 showed a very rapid disappearance of the two organisms, which passed 

 into the nose where their presence could be demonstrated by making 

 plate cultures of the nasal mucus. Enormous numbers of the Kiel 

 bacilli, introduced into the conjunctival sac, were all transferred to 

 the nasal cavity, on the average, by the end of half-an-hour. The 

 pyogenic staphylococci persisted on the surface of the conjunctiva 

 for a longer period, but they also passed in large numbers through 

 the lachrymal canal into the nose. 



Certain observers, notably Bernheim 2 , thought that the tears, 

 in addition to their purely mechanical defensive action, were capable 

 of destroying the micro-organisms by their microbicidal power. 

 Bach 3 submitted this question to a minute examination and came to 

 the conclusion that several species of bacteria, introduced in vitro 

 into the tears of healthy persons or of those who were suffering 

 from conjunctivitis or certain other ocular diseases, disappeared 

 somewhat rapidly. Comparative experiments with tears previously 

 heated to 58 and even to 70 C., in most cases gave the same 

 results, that is to say, they caused a rapid disappearance of the 

 organisms introduced. From these facts the author concluded that 

 it is probably to the salts contained in the tears that their bacteri- 

 cidal action is due. Control experiments made with physiological 

 saline solution and with various mixtures of mineral salts met 

 with in the tears have been found by Bach to cause a like 

 disappearance of the same species of organisms. Well water, and 



1 von Graefe's Arch.f. Ophth., Leipzig, 1894, Bd. XL, S. 130. 



2 Deutschmann's Beitr. z. Augenheilk, Hamburg u. Leipzig, 1893, Hft. vin. 



3 op. cit. supra. 



