314 ON GEOWTH AND OVERGROWTH 



4. Endothelial. 



Lining endothelium of blood-vessels, lymphatics. 



II. Hylic or Primitive Pulp Tissues 



Organs and tissues in which the special characteristic is that 

 the specific cells lie in, and are separated by, a definite stroma, 

 homogeneous, or fibrillar, in which there may or may not be blood 

 and lymph vessels. 



1. Epiblastic. 



Nerve cells, neuroglia. 



2. Hypoblastic. 



(Notochord. See note, p. 310.) 



3. Mesenchymatous. 



Fibrous connective tissues, cartilage, bone, reticulum of lymph 

 glands, bone marrow, fat cells, involuntary muscle tissue, 

 spleen, blood-vessels, blood corpuscles. 



4. Mesothelial. 



Striated muscle, including cardiac muscle. 



With this conception of the two great groups of tissues, we 

 can now proceed to classify the tumours, by which term I refer 

 here to what Thoma has called " autonomous neoplasms." Of 

 these there are two great orders, the Teratomata and the Blasto- 

 mata. The former I have elsewhere defined as " tumours 

 composed of the products of growth of one individual within 

 the tissues of another individual of the same species," the latter 

 as " tumours composed of the products of aberrant growth of 

 cells and tissues of the individual in whom they are developed." x 

 It is not necessary here to discuss the correctness of these defini- 

 tions, for, however defined, I wish here to leave the Teratomata 

 very largely out of consideration ; they form a class by them- 

 selves, and whether we accept or do not accept the definition 

 above given, we find that their mode of development and their 

 characteristics follow — with complications — the lines about to 

 be laid down with regard to the Blastomata. These latter form 

 the more important class, and it is with them that I wish specially 

 to deal. 



Following this scheme of the classification of the normal 

 tissues, we may now divide these into two main genera — the 



1 British Med. Journ., London, 1901, i. 621. See pp. 285, 286 of this 

 volume. 



