270 



THE MICROSCOPIST. 



(2.) Cavernous or venous angioma, erectile tumor, or 

 aneurism by anastomosis, is generally round, from the 

 size of a bean to that of a walnut. It is similar in struc- 

 ture to the erectile cavernous tissue of the penis and clit- 



FIG. 219. 



The substance of the cavernous tumor in full development. 1-300. From a cavernous 

 tumor of orbit. After RIXDFLEISCH. 



oris, consisting of a network of fibres containing blood 

 (Fig. 219). They are generally of a bluish color. Venous 

 angiomata, consisting mainly of enlarged and tortuous 

 veins, are often seen as internal or external hsemorrhoidal 

 tumors. 



(3.) Arterial angioma is sometimes met with, especially 

 in the branches of the temporal and occipital arteries. 



(4.) Lymphatic angioma is a similar dilatation of the 

 lymphatic vessels, and has been principally noticed in 

 connection with elephantiasis. Lymphangiomata of the 

 kidneys and of the skin have also been described. 



2. Thrombosis is a coagulation of the blood in the ves- 

 sels during life, from impeded blood-flow or changes (as 

 inequalities) in the walls of the vessels. It depends on 

 separation of the fibrin from the blood. Dr. Schmidt has 

 shown that the blood-corpuscles contain an albuminoid 



