Immimity of the skin and mucous membranes 431 



)f the female dog, rabbit and guinea-pig, was found to be neither 

 very marked nor very active. The micro-organisms introduced into 

 the vagina usually remained there for some time. Of all the factors 

 in the microbial destruction which Cahanescu was able to make out 

 that of the accumulation of leucocytes was the most active. Some- 

 times he observed an extraordinary amount of phagocytosis, whilst 

 in other experiments this was slight or even absent. Many of the 

 leucocytes being killed in the vaginal mucus, it is possible that in 

 some cases a certain bactericidal action of the cytases which have [452] 

 escaped from these dead leucocytes is set up. It is true that the 

 vaginal secretion of the mare did not exhibit this antimicrobial 

 property in vitro, but in the other animals experimented upon it 

 was found impossible to make similar experiments, the quantity of 

 mucus being too small. In woman the acidity of the surface of the 

 mucous membrane of the vulva and of the vagina, so frequently 

 present, may play a certain part in the protective action against those 

 bacteria which cannot tolerate the acid medium, but the animals 

 studied by Cahanescu, even female dogs, do not possess this advan- 

 tage, their mucous membranes usually having an alkaline reaction. 



In the urinary channels this acid reaction also plays a part, as one 

 of the defensive agencies against the penetration of bacteria. This 

 may also be effective in man and other animals that have an acid urine. 

 In many other animals, however, where the urine is alkaline micro- 

 organisms do not pass into the deeper parts of the urinary organ 

 under normal conditions. Here it is to the outflow of the urine that 

 the bladder owes its immunity against pathogenic micro-organisms 

 and saprophytes. When we connect two flasks containing steriUsed 

 broth in such a way that the fluid flows slowly from one of them into 

 the other, the former never becomes contaminated by the micro- 

 organisms which are present in the latter, in which latter the broth 

 is soon transformed into a ]fmree of bacteria, whilst in the foi-mer 

 the broth remains unaffected and aseptic. This purely mechanical 

 factor has been well brought out by Preobrajensky^ as the result 

 of work carried out in Duclaux's laboratoiy. The sterility of the 

 normal urinary bladder must be attributed to a similar cause. When 

 the urine begins to stagnate in the bladder it very readily becomes 

 contaminated. 



Since the acceptance of the view that the suprarenal capsules 

 serve to neutralise the effect of certain toxic substances elaborated 

 1 A7m. de Vlnst. Pasteur, Paris, 1897, t. xi, p. 699. 



