DISTRIBUTION AND HABITAT OF THE BACTERIA. 727 



spores, e.g. , those of bacillus subtilis, may live for 

 several months (compare p. 644). 



The secretions of the body also, more especially the Absence of 

 urine, are according to the investigations of Wyssoko- of C pl?ho 



witsch * free from bacteria, even when infective bacteria on . es ' in the 

 are present in the body and circulate in the blood. It 

 is only in the cases where there is plugging of the 

 vessels of the kidneys b} 7 masses of bacteria, and in con- 

 sequence necrotic patches with marked lesion of the 

 tissue, that we have an excretion of bacteria in the urine. 

 Such a state of matters is almost always seen after the 

 injection of staph. aureus into the blood, but these 

 bacteria do not appear in the urine soon after the 

 injection even when large numbers were introduced, but 

 only after deposits have been formed in the kidney and 

 have opened up artificial passages. 



Gunning f has examined the air expired by man for Absence of 

 bacteria. He found that when the air was expired 

 through a nutrient solution there was no infection of 

 the latter if only the entrance of saliva, &c., was pre- 

 vented. As a matter of fact we must, from what we 

 have learnt as to the detachment of bacteria from moist 

 surfaces (see p. 688), regard it as very improbable that 

 bacteria would be detached from the constantly moist 

 mucous membranes and carried with the current of 

 expired air which is constantly saturated with moisture. 

 Hence the only way in which we can conceive that 

 organisms present on the mucous surface of the respira- 

 tory tract can spread through the air, is that in speaking 

 and coughing small particles of fluids are detached, 

 expelled, and remain mixed for short distances with the 

 expired current of air, or that sputa dry up after their 

 expulsion, and are converted into dust. 



* Zeitschr.f. Hygiene, Bd. 1, Heft 1. 



f Klin. Monatbl.f. Angenheilk,, Jahrg-. 20, 1882, 



