8 THE TOXER LECTURES. 



well observed and nccurately recorded facts, and its excellent 

 atlas contains numerous faithful representations of appearances 

 which ma}'' readily be observed by those who take the pains to 

 follow his method of preparing sections. 



In December, 1867, Professor \Yaldeyer of Breslau published 

 in Virchow's Archiv * an elaborate essay on the development 

 of carcinoma, in which he endeavored to extend the views of 

 Thiersch to all other forms of cancer. For Waldej'cr there 

 are no essential differences between the so-called epithelial and 

 other cancers ; all are developed alike by the budding out of 

 cancer cylinders from some normal epithelial structure. The 

 cells of the cancer cylinders have everywhere a more or less 

 pronounced epithelial type, as in fact was pointed out by Vir- 

 chow as long ago as 1847.t 



The particular characteristics presented in any given case 

 are dependent to a great extent on the characters of the pe- 

 culiar epithelial structure from which the cancer cylinders have 

 originated. For example, in the case of cancer of the female 

 breast, which has so long served as the basis of our general 

 ideas of cancer, the cylinders sprout from the epithelium of 

 the ducts and terminal vesicles of the mammary gland, and 

 bud out into the surrounding connective tissue by a process 

 of growth which is only a pathological repetition of the proc- 

 esses by which the gland was first developed ; by which it 

 attains its feminine dimensions at puberty ; and by which it 

 acquires its temporary increase at each period of lactation. 

 Coincident with the development and growth of the cancer 

 cylinders, the small-celled brood makes its appearance in the 

 intervening connective tissue, but this is hy no means the es- 

 sential or significant part of the process. 



Cancers of the stomach originate in like manner from the 

 glands of the gastric mucous membrane which sprout through 



* Virchow's Archiv, Bd. 41, S. 470. Die Eiitwicklung der Carcinomc. 



t Virchow's Archiv, Bd. 1, S. 94. Zur Eutwiclilungsgeschichte des KrebscB. 



