152 Disturbances of Circulation. 



tomata (neoplasms, tumors) whose cells in the growth of the 

 mass are penetrating the walls of the blood vessels and, picked up 

 5y the blood flowing by, are carried along with the stream. Wher- 

 ever they lodge a new autoblastic growth develops from the multi- 

 plication of the displaced cells, which retain their power of growth. 

 Since usually it is not one single cell which is thus swept from the 

 primary site, but whole groups of cells being loosened and 

 separated from each other in the circulating blood and scattered 

 throughout the capillary network of the organ into which they are 

 carried, the latter becomes riddled with tumor nodules (disseminated 

 or multiple embolism). In dogs, for example, which are suffer- 

 ing from cancer of the thyroid gland the lungs are as a rule occu- 

 pied by great numbers of nodules of the same carcinomatous char- 

 acter, the cells having penetrated from the cancerous alveoli of the 

 gland into the thyroid veins and having of course been carried into 

 the lungs. In the same way from cancers of the mammary glands, 

 the skin, the nose, etc., after invasion of the tributaries of the vena 

 cava, metastatic nodules develop in the lungs. Intestinal, gastric 

 and pancreatic cancers give rise to metastatic embolism in the liver, 

 the tumor cells primarily gaining access to the portal vein ; only in 

 case they pass through this organ does the lung become involved 

 by the tumor cells. [This is true in a general sense provided the 

 hsemic route is followed in metastasis. It should be added however 

 that these cells may find their way by the lymph stream through 

 the thoracic duct to the lungs, the liver being entirely escaped. So, 

 too, it is possible by the minor anastomotic communications be- 

 tween the portal system and the general venous system, as by way 

 of the veins of the smaller gastric curvature, lower oesophageal 

 and azygos veins, that the cells may be conveyed to the lungs 

 directly, the liver being evaded.] 



Malignant bacterial emholisui is determined by the en- 

 trance of pathogenic bacteria into the blood vessels, quite com- 

 monly the pyogenic organisms ; more rarely the vegetable organ- 

 isms like the spores of moulds enter into consideration. Such 

 germs may gain entrance into the circulating blood through lesions 

 of the skin or mucous membranes. Lesions which were practically 

 imperceptible may serve as the point of entrance [it is also claimed 

 by a number of persons that in a limited degree bacteria may pass, 

 as it were be absorbed, through delicate mucous membranes with- 

 out the actual existence of any structural disturbance of the mem- 

 brane, as Ravenel has pointed out in case of tubercle bacilli passing 

 through the normal intestinal wall to the mesenteric glands], 



