296 BACTERIA PATHOGENIC TO MAN 



lucent in color, somewhat smaller than a millet seed in size, and hard! 

 in consistence. 



But miliary tubercles are not the sole tuberculous products. The 

 tubercle bacilli may cause the diffuse growth of a tissue identical in 

 structure with that of miliary tubercles that is, composed of a base- 

 ment substance, containing epithelioid, giant, and lymphoid cells. 

 This diffuse tubercle tissue also tends to undergo cheesy degeneration. 



DISTRIBUTION OF TUBERCLE BACILLI IN THE TISSUES. In acute 

 tuberculosis, especially when caseation is rapidly spreading, the bacilli 

 are usually abundant. They are generally scattered irregularly through 

 the tissues or in small groups. They are occasionally found in the 

 leukocytes and in the giant and epithelioid cells. In subacute and 

 chronic lesions they are usually few in number. Sometimes in old 

 caseous materials numerous stained granular points are seen; these 

 are supposed by some to be a resting stage similar to spores, but not 

 resistant to heat. 



USUAL POINT OF ENTRANCE OF INFECTION. Infection by the tubercle 

 bacillus takes place usually through the respiratory tract or the digestive 

 tract including the pharynx and tonsils, more rarely through wounds 

 of the skin. 



Tuberculosis may be considered to be caused chiefly by the direct 

 transmission of tubercle bacilli to the mouth through soiled hands, 

 lips, handkerchiefs, food, etc., or by the inhalation of fine particles of 

 mucus thrown off by coughing or loud speaking, or of tuberculous dust. 



TUBERCULOSIS OF SKIN AND Mucous MEMBRANES. When the skin 

 or mucous membranes are superficially infected through wounds there 

 may develop lupus, ulceration, or a nodular growth. The latter two 

 forms of infection are apt after an interval to cause the involvement of 

 the nearest lymphatic glands, and then finally the deeper structures. 



TUBERCULOSIS OF DIGESTIVE TRACT. Tuberculosis of the gums,, 

 cheeks, and tongue are rare, and usually occur through the germs enter- 

 ing lacerations caused by sharp, ragged teeth. The tonsils and pharynx 

 are somewhat more often involved. The stomach protected through 

 its acid gastric juice, and oesophagus by its epithelium, are almost never 

 attacked. The small intestines, rich in lymph glands, are rather fre- 

 quently the seat of infection from bacilli swallowed with the food. In 

 a striking case four previously healthy children died within a short 

 period of one another. Their nurse was found to have tuberculosis 

 of the antrum of Highmore, with a fistulotis opening into the mouth. 

 She had the habit of putting the spoon with which she fed the children 

 into her mouth so as to taste the food before it was given to them. As 

 already noted, the bacilli frequently pass through the mucous mem- 

 brane to the lymph glands without leaving any lesions. 



Intestinal and mesenteric tuberculosis, which is rather common witb 

 children, is due not only to swallowing the bacilli received in the above- 

 ways, from human sources, but also to the ingestion of tuberculous milk. 



TUBERCULOSIS OF RESPIRATORY TRACT. The lungs are the most 

 frequent location of tuberculous inflammation, in spite of the fact that 



