436 THE TUBERCLE BACILLUS GROUP 



the method of Vaughan, have isolated a non-specific poisonous sub- 

 stance from fat-free tubercle bacilli which kills guinea-pigs with 

 symptoms typical of anaphylaxis. The mineral constituents of 

 tubercle bacilli have been determined by de Schweinitz and Dorset. 1 



Toxins. The tubercle bacillus appears to elaborate both an endo- 

 toxin and an extracellular toxin. 2 The endotoxin causes necrosis, 

 caseous degeneration and general cachexia and stimulates tubercle 

 formation. The extracellular toxin causes fever and the acute inflam- 

 matory reaction observed around tubercles and tuberculous tissue 

 in tuberculous animals. Little or no effect is produced in healthy 

 animals except emaciation. The toxins liberated by the tubercle 

 bacillus are apparently on the whole rather mild, because they produce 

 as a rule only local lesions. This would indicate that the diffusion 

 of toxin is somewhat limited. Furthermore, the kidneys do not ordi- 

 narily exhibit anatomical changes which could be definitely ascribed 

 to the elimination of a tuberculous toxin through them. Whether 

 the cachexia, which is a prominent feature of advanced cases of 

 tuberculosis, is to be regarded as a purely toxic phenomenon is not 

 clear. Holmes 3 has suggested that the fatty acids of the tubercle 

 bacillus cause a lymphocytosis. 



Pathogenesis. Human. According to Naegeli, 4 rather more than 

 90 per cent, of adults who come to autopsy show scar tissue at the 

 apices of the lungs, which he believed were healed tubercles. Later 

 observations have not fully confirmed these figures, but it appears 

 that fully 50 per cent, of adults have healed tubercles at this site. 5 

 Frequently virulent tubercle bacilli have been isolated from the 

 centre of this scar tissue, but it should be remembered that occasion- 

 ally virulent tubercle bacilli have been isolated from bronchial lymph 

 nodes which appear to be normal. 



Modes of Infection. Hereditary Transmission. Transmission of 

 the tubercle bacillus through the sperm has never been established; 

 transmission through the ovum is also not definitely established. 

 The maternal blood, on the contrary, appears to be a vehicle through 

 which tubercle bacilli may pass, or grow through the placental barrier 

 and thus reach and infect the fetus. 6 



1 Jour. Am. Chem. Assn., 1898, xx, 618. 



2 Armand-Delille, Monographies Cliniques en Medicine, etc., 1911, No. G6, Paris. 



3 Guy's Hospital Reports, 1909, lix, 155. 

 " Virchow's Arch., 1900, clx, 426. 



5 Lubarsch, Virchow's Arch., 1913, ccxiii, 417. 



6 See Gartner, Ztschr. f. Hyg., 1893, xiii, 126-139, for summary and discussion of 

 early literature. Also, Schmorl and Geifel, Miinchen. med. Wchnschr., 1904, 1676. 



