534 Tuberculosis. 



From the tuberculous foci in the lungs the virus passes 

 from the bronchioles to the larger bronchial tubes and the 

 neighboring healthy alveoli. Thus the diseased area becomes 

 larger and larger. Secretions containing bacilli are coughed 

 up and lodge on the mucous membrane of the trachea and 

 larynx, especially on the ventral surface immediately posterior 

 to the attachment of the vocal chords. Thus the tuberculous 

 process gains a foothold here.; These secretions may also reach 

 the mouth whence they reach the small intestine with the food, 

 causing the development of tuberculosis of the mucous mem- 

 brane, especially of the ileum. Tubercles and ulcers that are 

 occasionally found here are usually produced in this manner. 

 In a similar manner a metastatic process in the renal paren- 

 chyma may spread to the pelvis of the kidney and follow the 

 course of the ureters downward. On the other hand primary 

 infection of the uterus, the vagina, the epididymis and the 

 bladder may spread into the pelvis of the kidney and from 

 there attack the parenchyma. 



If the bacilli enter the vessels they are transported by 

 the blood stream and, if not destroyed, produce embolisms in 

 various organs from which tubercles are developed. This is 

 comparatively frequent in the kidney and spleen. If the number 

 of bacilli entering the blood stream is excessive, numerous 

 tubercles may develop in several organs and give rise to an 

 acute miliary tuberculosis (tuberculosis miliaris acuta). This 

 happens most frequently when tubercles which develop in the 

 walls of arteries or veins of an infected organ, degenerate or 

 develop into ulcers from which the bacilli pass into the blood 

 stream. This danger is particularly great if the vessel com- 

 municates by a direct opening with a nearby or adjacent cheesy 

 focus. Exposed tubercles in the walls of the thoracic duct may 

 also be the cause of infection of the blood stream. (Joest re- 

 ported two cases of open tuberculosis of the thoracic duct in 

 cows.) 



If bacilli are discharged into the lumen of a peripheral 

 vein or into a branch of the pulmonary artery most of the 

 bacilli will lodge in the lungs and produce tubercles almost 

 exclusively in these organs. On the other hand if tuberculous 

 ulcers exist in one of the pulmonary veins the bacilli which they 

 discharge may enter any organ of the body that are reached 

 by blood from the left ventricle and there produce a miliary 

 tuberculosis, most commonly in the spleen, liver and kidneys. 



According to Eoemers' experiments, which were confirmed by Hamburger, 

 Courmont & Lesieur and by Leber, the body of a tuberculous animal offers more 

 or less resistance to subsequent external infections. Such additiojial external 

 infections are either successfully resisted or they have only a local effect; they may 

 even have a curative effect, as had already been shown by Koch. On the other 

 hand, after infection with large masses or virulent bacilli lung cavities may deve'op 

 instead of miliary tuberculosis. Calmette & Gu^rin demonstrated such an increased 

 resistance in tuberculous cattle. In these animals the injection of highly virulent 

 bovine bacilli produced chronic processes only. This increased power of re'^istfince 

 is said to manifest itself also toward bacilli from the body of the animal itself 



