306 ON GROWTH AND OVERGROWTH 



knowledge, manv cases were discovered which did not fit into this 

 scheme. A classification which brings together unlike bodies, 

 making them members of one group, is, on the face of it, in- 

 adequate and faulty. Now, more especially during the last ten 

 years, pari passu with a recognition of the bearing of the fuller 

 and more recent findings of the embryologists, this classification 

 has been found to have the above failing. It is, for example, 

 generally accepted that the specific and characteristic cells of 

 several tissues of the glandular type — of the kidneys, suprarenal 

 bodies, ovaries, testes, and uterine mucosa — are of mesoblastic 

 origin, but these, nevertheless, give rise to tumours which may 

 and often do resemble most closely those of hypoblastic and 

 epiblastic origin. 



There has been grave doubt as to the embryogeny of the 

 organs in question. The idea that tissues of glandular type can 

 only be derived from the two primary cell layers is very firmly 

 fixed, and in one direction the attempt has been made to show 

 that the organs in question are of hypoblastic or epiblastic origin ; 

 on the other, to make out the distinction between these organs 

 and what have been termed " true glands." But I am only 

 expressing the general opinion of modern embryologists and 

 histologists when I say that all these organs now are accepted 

 by the majority as being definitely derived from mesoblast. 

 And thus the cancer-like tumours which originate in these organs 

 must be accepted as being mesoblastic. 



On the other hand, the gliomata have a structure which 

 brings them into close alliance with the atypical or malignant 

 connective tissue tumours, and yet the neuroglia, from which 

 they are derived, is of epiblastic origin. The notochord, again,' 

 is an organ of hypoblastic origin. According to Ribbert, and the 

 view is becoming accepted, the remains of this foetal organ may 

 give rise to tumours somewhat resembling myxomata, 1 that is 

 to say, to tumours which, though of hypoblastic origin, are of 

 connective tissue type. Histologically, and for practical purposes, 

 the first series above mentioned ought to be grouped along with 

 the adenomata and carcinomata, and the second with the sarco- 

 mata and connective tissue tumours, but the old embryological 

 classification forces us to make the very opposite arrangement. 



1 Tumours of mucoid type, resembling the connective tissue of the foetus 

 as seen in " Wharton's jelly " of the umbilical cord. 



