382 Tumors. 



The cells of an endothelionia present the same polygonal, 

 flattened, fusiform and polyhedral forms as the fibroblasts and 

 angioblasts, the cells of the blood and lymph vessels being, in 

 fact, formed originally of the same material. In the tumors they 

 are arranged as scales, or in cylindrical cords or in hollow tubu- 

 lar manner so as to form a network with thickened nodal points, 

 and are supported by a vascular stroma. The microscopic appear- 

 ance is therefore very like that of an alveolar sarcoma or carci- 

 noma; sometimes the arrangement of the cells in lamellae may be 

 concentric like the tunic of an onion. 



Those endotheliomata which take their origin from the outer 

 coat (adventitia) of the bloodvessels (from the perithelial cells) 

 and are recognized as forming mantles of tumor cells about the 

 blood vessel and its branches, are generally spoken of as pcri- 

 theliomata. 



Retrograde changes which occur in endotheliomata may give 

 an unusual appearance to some forms, in consequence of which 

 special names are applied. As an example the cylindrical cords 

 may undergo, hyaline degeneration of their endothelial cells, be 

 transformed into shining homogeneous structures, standing out 

 conspicuously in transverse section like hyaline, concentrically 

 laminated balls or masses ; this appearance has led to their being 

 called cylindroniata. In other instances calcareous deposits (in 

 the form of globules, needles and club-shaped masses) occur in 

 the structure of the growth, giving a grittiness to the tumor in 

 section and making the cut surface rough and sandy ; these are 

 especially met in the brain and are known as psammomata {acer- 

 vuloma, sand tumor). The endotheliomata which -develop from 

 the choroid plexus of the brain are always richly infiltrated with 

 cholesterin deposits, and are called in a superficial way choles- 

 teatomata. 



However these changes or depositions which give occasion for the special 

 names indicated are not absolutely restricted to one particular type of tumor. 

 In the collection of lime and cholesterin it must be kept in mind that the 

 cells of the neoplasm are preserving qualities of the cells from which they 

 had their derivation, for brain sand and cholesterin are found normally also 

 in the pineal gland and in the choroid tissue. True epithelial tumors, how- 

 ever, which occur in the cranial cavity and are referable to inclusions of 

 epidermoidal rests usually contain cholesterin, and it is also met in dermoid 

 cysts or epidermoid cysts of the subcutaneous tissue; these types requiring 

 the acceptance of a further class, the epithelial cholesteatomata. 



Contributions recording the' occurrence of endotheliomata in 

 animals are very meagrely found in literature. Dexler met in a 



