26 CLINICAL APPLIED ANATOMY. 



may be expected in this situation. Others will pass on through 

 the left side of the heart and he generally distributed by the 

 arterial system. 



If a pulmonary vein he the place of entrance the infection will 

 sweep on directly to the general arterial system and be dis- 

 tributed to the organs this supplies. Generally the brunt of the 

 infection will be borne by those organs which are most richly 

 vascular, such as the spleen, liver, and kidney. The lung will be 

 invaded along the bronchial arteries, and so to a comparatively 

 slight extent. 



A focus of infection in the portal vein area will chiefly infect the 

 liver, and an} 7 bacilli which find their way through this barrier 

 will emerge by the hepatic veins and find a resting-place in 

 the lungs. It is well to remember that the liver may be 

 infected through the hepatic artery when bacilli are in the 

 arterial blood stream. 



When the endocardium or the aorta are involved the route of 

 infection is by all the systemic arteries, but when a small arterial 

 trunk is invaded, which may occur when tuberculosis is active 

 in such organs as the lungs and kidneys, the micro-organisms 

 will settle as infarcts in the terminal distribution of the vessel 

 involved. 



The great serous sacs are but scantily supplied with blood- 

 vessels, so the peritoneum, pleurae, and pericardium do net show 

 a profuse depo.sit of tubercles in blood infections. The choroid, 

 although small, is very vascular, and tubercles deposited in it 

 may sometimes be seen with the ophthalmoscope. The actively 

 growing tissues of children, with their free blood supply, afford a 

 good nidus for bacilli when the latter have once entered the blood 

 stream. 



In disseminated blood tuberculosis the bacilli are in the vessels, 

 and therefore, despite the copious deposits in the lung mentioned 

 above, they will not be found in the expectoration unless there 

 be an old pulmonary focus, or, as sometimes happens, the disse- 

 minated foci are of different ages, and some of the older deposits 

 have gained access to the air-passages. Deposits of different 



