252 THE INFECTIOUS DISEASES. 



victims of this disease, both men and auimals, are apt, as stated above, 

 to throw off enormous numbers of the bacilli in the sputum and other 

 excreta, the germ is widely dispersed in inhabited regions, especially in 

 buildings frequented by uncleanly tuberculous persons or by infected 

 cattle. 



Among the lower animals, guinea-pigs, rabbits, monkeys in cor.fine 

 merit, and cattle are particularly susceptible to the action of the tubercle 

 bacillus. Although tuberculosis is widespread in man, he is not, as com- 

 pared with some of the lower animals, particularly susceptible. While 

 the tuberculous process presents some special differences in different 

 animal species in rate of development, amount of necrosis, tendency to 

 softening, calcification, etc., the fundamental effects are similar in man 

 and in the lower animals. 



SOURCES OF THE TUBERCLE BACILLI, PORTALS OF ENTRY, AND 

 DISTRIBUTION OF LESIONS. 



Congenital tuberculosis has been observed, but it is apparently quite 

 infrequent. ' Tubercle bacilli are most frequently transmitted to the well 

 from the victims of tuberculosis by means of the sputum which is cast 

 off, allowed to dry, and becomes pulverized and is then inhaled as dust. 



Many observations on the occurrence of tuberculous bronchial lymph- 

 nodes in persons exhibiting no appreciable tuberculous lesions elsewhere 

 would indicate the probability of access of the bacilli to the lymph chan- 

 nels without primary lesion at the portal of entry. A considerable per- 

 centage of persons dying from other diseases have been found to have 

 tuberculous lesions often healed in the lungs or bronchial lymph-nodes. 2 

 In adults the lungs, in children the bronchial lymph-nodes are the most 

 frequent seat of tuberculous lesion. 3 



While the inhalation of dust containing dried tuberculous sputum is 

 the chief means of infection under the ordinary conditions of modern 

 life, other modes of conveyance of the infective bacilli are of importance. 4 

 It has been shown that pathogenic bacteria, and among these the tubercle 

 bacilli, may enter the lymphatics through the intestinal mucosa without 

 demonstrable lesions in the latter. There is no doubt that the bacilli 

 may be introduced into the alimentary canal by contaminated milk and 

 meat of tuberculous cattle. 5 



For a study of placcntal and congenital tuberculosis see Warthin atd Coicic, Jour, 

 of Infec. Dis., vol. i., 1903. p. 140. 

 ' 2 See reference, Naegeli, p. 251. 



3 See reference, Northrnp and Bmaird, p. 398. For a study of the distribution and 

 origin of tuberculosis in children see Guthrie, Lancet, February 4th, 1899, p. 286; also 

 Hand, Proc. Path. Soc. Phila., March, 1903. 



4 For a study of tubercle bacilli on books, see Mitulescu, Zeitschr. f. Hygiene u. 

 Infkr., Bd. xliv., p. 397, 1903. 



5 See Kober, Amer. Jour. Med. Sc., vol. cxxvi., 1903, p. 684, Bibl. For the intercom- 

 municability of human and bovine tuberculosis, see Havenel, Proc. Path. Soc. Phila- 

 delphia, May, 1902. 



Consult for his views on the intestine as portal of entry for the tubercle bacillus, 

 Behring, Deutsch. med. Wochenschr., September 24th, 1903; summary in British Med. 

 Jour., October 17th, 1903, p. 993. For reference to primary tuberculous enteritis see 

 footnote, p. 553. 



