THE TUBERCLE BACILLUS 593 



known as "Nahrstoff Heyden/' upon which tubercle bacilli are said to 

 proliferate more rapidly than other bacteria. His method has yielded 

 excellent results. It is prepared as follows : 



' ' Nahrstoff Heyden " - 10 grams 



Sodium chlorid 5 ' ll 



Glycerin 30 " 



Ag-ar 10 l ' 



Normal sodium solution 5 c.c. 



Aq. dcst 1,000 < ' 



Biological Considerations. The tubercle bacillus is dependent 

 upon the access of oxygen. Its optimum temperature is 37.5 C. 

 Temperatures below 30 and above 42 C. inhibit its growth. In fluid 

 media, the bacilli are killed by 60 in fifteen to twenty minutes, by 80 

 in five minutes, by 90 in one to two minutes. They will withstand dry 

 heat at 100 C. for one hour. They are resistant to cold. The com- 

 paratively high powers of resistance of the bacillus are attributed to the 

 protective qualities of the waxy cell membrane. 21 



The life of cultures, kept in favorable environment, is from two to 

 eight months, varying to some extent with the nature of the culture 

 medium. The viability of the bacilli in sputum is of great hygienic 

 importance. In most sputum they may remain alive and virulent for as 

 long as six weeks, in dried sputum for more than two months. 22 



Five per cent carbolic acid kills the bacilli in a few minutes. 23 Used 

 for sputum disinfection, where the bacilli are protected, complete disin- 

 fection requires five to six hours. Bichloride of mercury is not very 

 efficient for sputum because of the formation of albuminate of mercury. 

 Direct sunlight kills in a few hours. 



Pathogenicity. The tubercle bacillus gives rise in men and sus- 

 ceptible animals to specific inflammations which are so characteristic 

 that a diagnosis of tuberculosis may be made by histological examina- 

 tion, even though tubercle bacilli themselves are not found. These 

 foci, known as tubercles, were first studied in detail by Baumgarten, 24 

 and, since then, have been the object of many pathological investiga- 



20 " Nahrstoff Heyden ' ; is prepared in Germany. It is a white powder similar 

 to nutrose. 



21 Tli. Smith, Jour. Exper. Med., 1899 ; Grancher et Ledoux-Lebard, Arch, de 

 med. exper., 1892; Galtier, Compt. rend, de 1'acad. des sci., 1887. 



22 Schell und Fischer, Mitt. a. d. kais. Gesundheitsamt, 1884. 



23 De Toma, Ann. di med., 1886. 



* 4 Baumgarten, Bcrl. klin. Woch., 1901. 



