I 



INFECTION. 99 



We know that the fission-fungi have a boring movement, and 

 that this is apparently in a forward direction ; the question is, Is 

 it strong enough to penetrate these line capillaries ? 



The answer is, "We do not know ! 



Again, some authorities have described openings, or vacancies, 

 between the individual epithelium cells lining the alveoli, and 

 have looked upon them as the endings of the pulmonary lymph 

 system. 



If such stomata or openings really exist, they offer a natural 

 and favorable atrium to the penetration of bacteria into the system 

 by means of the lungs. 



As we have said, but a very small number can certainly pene- 

 trate so deeply as the alveoli ; but we know that, on account of the 

 wonderful degree of proliferation, a very small number is sufficient 

 to produce infection. 



The blood, from its chemical composition, and the presence of 

 oxygen, united with the temperature of the body, offers the most 

 favorable condition for the multiplication of bacteria. 



As to the intestinal tract, we have already said that the nature 

 of the mucosa is such that we do not believe it possible for the bac- 

 teria to penetrate its different membranes. 



The acidity of the stomach offers very unfavorable conditions to 

 the life or multiplication of germs. 



Some have.assumed, and among them the ablest of mycologists, 

 that an abrasion (wounding) of an intact surface is necessary to the 

 entrance of bacteria into the system. When we reflect on the mi- 

 nuteness of these objects, and how frequently results of this nature 

 may take place, both in the respiratory, and particularly the digest- 

 ive tract, we find good grounds for accepting this hypothesis as the 

 one favoring the general way in which infection takes place. 



Slight abrasions of the mucosa of the nostrils, pharynx, cheeks, 

 etc., or even that of the oesophagus, stomach, and intestines, are very 

 common with our own species : how much more so in our domestic 

 and other animals which seek their food in a natural manner, or re- 

 ceive it from the none too careful hands of man ! 



An unhealthy mucosa is of itself seldom intact ; abrasions of its 

 epithelial covering are very common, even though they do not occa- 

 sion such disturbances as to lead one to suspect any very serious 

 trouble. The proneness of the ruminantia to take up all sorts of 

 foreign objects — nails, hair-pins, broken glass, and even knives and 

 forks — is well known to many. 



Traumatic inflammation of the stomach and heart are no uncom- 



