Cancer. 401 



structures, lead to marked chronic enlargement of the glands 

 (lympJwgciioiis cancer metastases), one of the clinical character- 

 istics of the cancerous affection. Passing from the lymph glands 

 the cells of the growth may hy following the course of the efferent 

 lymph vessels, pass into the blood (anterior vena cava) ; or they 

 may gain entrance to the blood by direct penetration of the blood 

 vessel wall in their growth. In either event the cells are carried 

 onward with the blood stream and form new foci wherever they 

 may lodge in the capillaries and give rise to the formation of nodes 

 (hcrmatogeiious, eiiibolic cancer metastases). 



]\Ietastatic nodes are as a rule round, and multiple or dissemi- 

 nated because the cells have been widely scattered through an ex- 

 tensive area of vascular distribution. As a rule they are first sit- 

 uated in the lungs, because the cells are very likely to penetrate 

 into a vein and be carried throiigh the right heart and into the 

 lungs ; in case of primary cancer of the stomach, intestine or pan- 

 creas the liver is apt to be involved, by convection through the por- 

 tal vein. Should isolated cells pass through the pulmonary capil- 

 laries and get into the general circulation b}- way of the leff heart, 

 other portions of the body, as the spleen, kidneys or bones, may be 

 involved by dissemination of the metastatic cells. Sometimes, too. 

 when these cells .penetrate into bloodvessels they grow into cord- 

 like processes along the vascular lumen ; solid plugs of cancer cells 

 as thick as lead pencils may occasionally be found extending in 

 the thyroid veins from a cancer of the thyroid gland, even down 

 into the thoracic cavity. The vascular lumen becomes more or less 

 obstructed and the secondary thrombi formed are verv likclv to be 

 invaded by the cancer cells. 



As the tumor enlarges it compresses and pushes aside all the 

 elements of the organ with which it comes in contact ; in their pene- 

 tration into the deeper tissues and by their lateral extensions the 

 cellular roots of the cancer distend and occupy the lymph spaces, 

 pushing aside whatever gland-tissue, muscle or nerve may be 

 present, spreading out beneath the epithelial covering of mucous 

 membranes or integument and perforating layers of epithelium which 

 they may encounter. Pressure atrophy and necrosis of the surround- 

 ing tissue and tissue-destruction from the accompanying inflamma- 

 tion result from the cancerous infiltration, even hard bone and 

 cartilage, perhaps, being broken down by these changes. As the tu- 

 mor tissue nniltiplies beneath the epithelial la\ er of a surface it raises 

 it up, spreads out in larger and larger area close to the surface 



