BACILLI IN CHRONIC INFECTIOUS DISEASES. 413 



He concludes that the tubercle bacillus does not form endogenous 

 spores, such as are found in various other bacilli, but that in the rods 

 and branched filaments certain objects are seen which are probably 

 reproductive elements, and which closely resemble similar bodies 

 (" Kolben ") seen in the actinomyces fungus, to which Jones believes 

 the tubercle bacillus is closely related. 



Prudden and Hodenpyl (1891) have shown that the injection of 

 dead tubercle bacilli in rabbits gives rise to the development of nod- 

 ules in the lung containing epithelioid and giant cells, but that these 

 never undergo caseation. This fact is supposed to justify the infer- 

 ence that caseation is due to the products elaborated during the 

 growth of living tubercle bacilli. The results reported by Vissmann 

 (1892) correspond with those reported by Prudden and Hodenpyl. 

 Gamaleia (1892) has also obtained nodules with epithelioid and 

 giant cells from the injection of dead tubercle bacilli, but in his ex- 

 periments he also found caseation of the nodules. Baumgarten sug- 

 gests that this was probably due to the fact that there were some liv- 

 ing tubercle bacilli remaining in the cultures which he injected. 



Loomis (1890) and Pizzini (1892) have shown that living tubercle 

 bacilli are not infrequently found in the bronchial glands of individ- 

 uals who present no evidence of tubercular disease of the lungs or else- 

 where. The author last mentioned inoculated thirty guinea-pigs 

 with the bronchial, mesenteric, and cervical glands of thirty in- 

 dividuals in whom death was due to accident or acute disease, and 

 who were free from tuberculosis. Twelve of these thirty guinea- 

 pigs developed tuberculosis as a result of the inoculation. 



Straus (1894) has found tubercle bacilli in the nasal cavities of 

 healthy individuals. 



Ernst (1895), as the result of extended researches made under the 

 auspices of the Massachusetts Society for Promoting Agriculture, 

 has arrived at the following conclusions with reference to the pres- 

 ence of the tubercle bacillus in the milk of tuberculous cows : 



" The possibility of milk from tuberculous udders containing the 

 infectious element is undeniable. 



" With the evidence here presented, it is equally undeniable that 

 milk from diseased cows with no appreciable lesion of the udder may, 

 and not infrequently does, contain the bacillus of the disease." 



De Schweinitz (1894) has found that by continued cultivation in 

 an artificial medium the tubercle bacillus becomes attenuated, so that 

 when inoculated into guinea-pigs these animals give no evidence of 

 tubercular infection for six months or more. And his experiments 

 indicate that animals which have survived an inoculation with the 

 attenuated tubercle bacillus acquire an immunity against the patho- 

 genic action of virulent cultures. 



