478 THE TUBERCLE BACILLUS GROUP 
modified, perhaps by a fat-splitting enzyme (lipase); then develop- 
ment takes place. It should be remarked parenthetically that poly- 
morphonuclear leukocytes which occasionally engulf tubercle bacilli 
do not contain lipase;^ these leukocytes may transport the organisms 
to lymphoid tissue or other tissue where eventually the bacilli escape, 
thus establishing new foci. Mononuclear leukocytes appear to contain 
lipase, as do certain fixed phagocytic cells in the alveoli of the lungs. 
Lenk and Pollak- and Wiener^ appear to have found active proteo- 
lytic ferments in tuberculous exudates. Opie and Barker^ have shown 
that the mononuclear epithelioid cells contain an enzyme which digests 
protein in a slightly acid medium; it is practically inert in an alkaline 
medium. Jobling and Petersen^ have found that the inhibition of 
enzyme action in caseous tubercle foci is apparently due to unsaturated 
fatty acids. Saturation of these acids with iodine causes an accelera- 
tion of the activity of the ferments. 
The primary lesions usually tend to progress slowly. Secondary 
invasion by tubercle bacilli through the lymph and bloodvessels 
frequently occurs, causing tuberculous foci in various ducts and 
glands of the body, as the bronchi, alveoli of the lungs, spleen, liver, 
tubules of the kidney, and in the genito-urinary system, particularly 
the epididymis and testicle of the male and the Fallopian tubes in the 
female. Involvement of the adrenals leads to the condition known as 
Addison's disease. The glandular organs are those most commonly 
infected, and of these the lungs and lymph nodes are most frequently 
involved; also the spleen, kidneys, liver, meninges both of the cord and 
brain, the pleural and pericardial cavities, the genito-urinary apparatus, 
and, less frequently, joints and bones. The muscles are only very 
rarely invaded. Various clinical names have been applied to tuber- 
culosis of different tissues: tuberculosis of the lungs is commonly 
designated consumption; of the spine. Pott's disease; of the cervical 
lymph glands, scrofula; and of the skin, lupus. The characteristic 
initial lesion is a small nodule or tubercle which may imdergo secon- 
dary changes, as caseation, calcification, ulceration, or various types 
of sclerosis. In the lungs the first organisms that reach the alveoli 
may leave no trace. They are dissolved there apparently, but may 
produce no progressive lesion. A second invasion in the same area 
frequently causes a local inflammation which usually results in infec- 
tion, apparently because the body has been sensitized by the first 
bacilli that entered, and in some way is rendered locally susceptible 
to the organism. 
The irritation caused by the extracellular toxin excreted by the 
tubercle bacillus brings about a response on the part of the tissues 
which is protective, as is manifested by a walling off of the bacilli. 
> Fiessinger and Marie : Compt. rend. Soc. de Biol., 1909, 67, 177. Bergelh Miinchen. 
med. Wchschr., 1909, 56, 64. 
2 Deutsch. Arch. klin. Med., 1910, 109, 350. ^ Biochem. Ztschr., 1912, 41, 149. 
4 Jour. Exp. Med., 1908, 10, 645; 1909, 11, 686, 
^ Ibid.. 1914, 19, .383. 
