316 ON GROWTH AND OVERGROWTH 



2. Hypohyloniata. 



Tumours derived similarly from embryonic pulp of hypoblastic 

 origin. 



(?) Chordoma. 



3. Mesohyloniata. 



A. Mesenchymal Hylomata. — Derived from tissues originating 

 from the persistent mesoblastic pulp or mesenchyme. 



(a) Typical. — Fibroma, lipoma, chondroma, osteoma, 



myxoma, leiomyoma. 



(b) Atypical. — Sarcoma (derived from mesenchymatous 



tissues), with its various subdivisions, fibrosarcoma, 

 spindle - cell sarcoma, oat - shape cell sarcoma, 

 chondro- sarcoma, osteo- sarcoma, myxo - sarcoma, 

 melanotic sarcoma, etc. 



B. Mesothelial Hylomata. — Tumours which are overgrowths 

 similarly of tissues derived from embryonic pulp of definitely 

 mesothelial origin. 



Rhabdomyoma. 



It will be seen that in this classification I do not include 

 the deciduoma malignum. As I have pointed out elsewhere, 1 

 accepting the view that the syncytium is of foetal origin and 

 not maternal, these tumours have to be classed with the Tera- 

 tomata, i.e. with the tumours originating in the growth of the 

 cells of a second individual within the tissues of an individual 

 of the same species. 



If this classification be studied, it will be seen that we have 

 done away with that deficiency in the earlier embryological 

 classifications whereby tumours of unlike orders and histological 

 appearances were grouped together and those of like characters 

 separated. Gliomata, for example, come to be placed close to 

 the mesenchymatous tissues ; the gland-like tumours of meso- 

 blastic origin become grouped along with those of epiblastic 

 and hypoblastic origin. 



Have we, in accomplishing this, introduced any new diffi- 

 culties ? One objection will undoubtedly present itself, namely, 

 that among the Mesolepidomata we have grouped together 

 tumours some of which are of a strongly epithelial or glandular 

 type, for example, the cancers of the uterus, with others like the 

 endotheliomata, which tend to be distinctly of a sarcomatous 

 type. But further consideration will show that this, instead of 



1 Loc. cit. See pp. 286 and 326 of this volume. 



