152 MANUAL OF BACTERIOLOGY. 



the most careful search fails to reveal the place at which the 

 bacteria entered. The bacilli of plague usually produce no 

 reaction at the point of entrance. 



It is probable that tubercle bacilli may pass through thin 

 epithelial surfaces and lodge in the deeper structures underneath, 

 where they produce definite lesions. For example, they may 

 pass by the lungs and enter the bronchial glands, and form 

 tubercles in that situation. 



Experiments on animals have shown that bacteria may be 

 very rapidly disseminated after their introduction. The inocu- 

 lation of mice, for instance, with anthrax bacilli has been known 

 to prove fatal, although the wound was washed immediately 

 with the strongest antiseptic solutions or the part amputated 

 within a few minutes. 



The manner in which infectious agents reach human beings 

 varies considerably. Generally speaking, the most important 

 element will be found to be direct or indirect connection with 

 another case of the same disease. W. H. Park was able to 

 cultivate diphtheria bacilli from bedclothing soiled by the 

 expectoration of diphtheria cases. Baldwin has shown that 

 tubercle bacilli may be found on the hands of patients having 

 pulmonary tuberculosis, especially those who expectorate on 

 handkerchiefs. Winslow found bacillus coli communis on 

 the hands of 5 per cent, to 19 per cent, of those examined; 

 his observations suggest the possibility that typhoid bacilli can 

 be carried in a similar manner. 



Air. — Excepting under certain special conditions, the air will 

 not contain the germs of disease. The dried pulverized 

 sputum of cases of pulmonary tuberculosis may float in the 

 atmosphere as dust which will contain tubercle bacilli. Fliigge 

 states that powerful expiratory efforts like coughing and sneez- 

 ing may carry tubercle bacilli with small particles of secretion 

 into the air, and that they may remain in suspension some time. 

 The pus-producing bacteria may be present in dust. In- 



