TUBERCLE BACILLUS 477 
and swine. The muscles are usually not invaded. No meat from 
tuberculous animals can be offered for sale in the public markets, 
however. 
Lipschultz^ has reported a case of cutaneous infection by the avian 
tubercle bacillus in man which resembled leprosy anatomically. The 
diagnosis was arrived at only after an exhaustive study of the organism. 
Infection of man with the avian tubercle bacillus is uncommon. 
The mechanism of infection with the tubercle bacillus has been the 
subject of much controversy.- It is apparent that the acid-fastness 
of the organism yer se does not confer pathogenic properties upon the 
organism because other non-pathogenic acid-fast bacteria are unable 
to induce progressive disease from man to man or from animal to 
animal. Acid-fastness, however, may be an initial factor in patho- 
genism, an opening wedge as it were, for it appears to be well estab- 
lished that acid-fast bacteria are relatively insoluble in body fluids 
and remain unchanged for considerable periods of time when they 
are introduced into the animal body. Theobald Smith'^ has advanced 
a tentative hypothesis which explains satisfactorily many of these phe- 
nomena. As tubercle bacilli reach the body (and as they escape 
from the body) they are surrounded by a protective envelope which 
causes the organism to behave somewhat as an inert foreign body 
until it finally settles dowTi in some structure where it can grow. 
The envelope is then slowly removed or modified by the action of 
normal tissue fluids and growth commences. He has also made the 
important suggestion that human tubercle bacilli tend to invade the 
tissues through the lymphatic system. The organisms pass to lymph 
nodes, and, if they escape to the lungs, or less commonly, to other 
organs, as the kidneys, intestines, testicles or uterus, which are in 
free communication with the exterior of the body, establish the host 
as a menace to others. If the bacilli find lodgment in a particu- 
larly susceptible host, the process may be rapid, leading to generalized 
tuberculosis with no significant escape of tubercle bacilli to the exterior. 
If, on the other hand, the process is stopped within the lymphatic 
sj'stem, the infective agent lies dormant or eventually perishes. In 
this manner strains of the average human virulence tend to become the 
prevailing type.* In this connection it is interesting to note that young 
tubercle bacilli are frequently non-acid-fast,* and that the tissues 
usually invaded by the bacilli — lymphoid tissue and the lungs— con- 
tain active lipase.'^ If this supposition is correct, the tubercle bacillus 
may remain latent in the body until the fatty capsule is removed or 
> Arch. f. Dermat. u. Syph., June, 1914, vol. 120. 
2 See The Spread of Tuberculous Infection in the Body, by Allen Krause, Am. Rev. 
Tuberc, 192-1, 9, 83. 
3 Jour. Am. Med. Assn., 1900, 46, 1247. ' Ibid., 1917, 68, 669. 
6 Wolbach and Ernst: Jour. Med. Res., 1903, 10, 313. 
6 Bradley: Jour. Biol. Chem., 1913, 13, No. 4. Briscoe: Jour. Pathol, and Bacteriol., 
1908, 12, 66. Bartel and Neumann: Centralbl. f. Bakteriol., orig., 1909, 48, 657. 
Zinsser and Carey: Jour. Am. Med. Assn., 1912, 58, 692. 
