90 LECTURE III. 



has been rendered by natural philosophers. At the time 

 when theromorphism played a conspicuous part, and 

 many analogies were discovered between pathological 

 processes and the normal states of inferior animals, com- 

 parisons also began to be instituted between new for- 

 mations and familiar parts of the body. Thus, Johann 

 Friedr. Meckel, the younger, spoke of mammary and 

 pancreatic sarcoma. What has very recently been 

 described in Paris as heteradenia (Heteradenie), or a 

 heterologous formation of glandular substance, was in 

 the school of the natural philosophers a pretty generally 

 accepted fact. 



Since the study of embryology has been prosecuted in 

 a more histological manner, the conviction has gradually 

 more and more been acquired, that most new formations 

 contain parts which correspond to some physiological 

 tissue, and in the micrographical schools of the west a 

 certain number of observers have come to the conclusion, 

 that in the whole series of new formations there is only 

 one particular structure which is specifically different 

 from natural formations, namely cancer. With regard 

 to this, the most important points urged are, that it 

 differs altogether from every other tissue, and that it 

 contains elements sui generis, whilst, singularly enough, 

 a second formation, between which and cancerous tissue 

 the older writers were wont to draw parallels, namely 

 tubercle, has although to it too nothing strictly analo- 

 gous could be discovered been much neglected, owing 

 to its having been regarded as an incomplete and some- 

 what crude product, and as a structure which had never 

 become properly organized. Yet, upon a more careful 

 examination of cancer or tubercle, we shall find that 

 everything depends upon our searching for that stage in 

 their development, in which they are exhibited in their 

 perfect form. We must not examine at too early a 



