486 



sondere Bedeutung unterzulegen und also, wie mein Vorschlag lautet, 

 eine Struktur als mechanisch im engeren Sinne zu bezeichnen, wenn 

 durch ihre Elemente Achsen von Spannungsellipsen (bezw. Spannungs- 

 ellipsoiden) insubstantiiert erscheinen. 



Die Anschauungen, zu denen ich gelangt bin, weichen von denen 

 Roux' ab, sie sind indessen, was ich nicht verkenne, auf einem durch 

 die Arbeiten Roux' geebneten Boden entstanden, und die Differenz ist 

 zwar nicht nur, aber doch vorwiegend formaler Natur. 



Greifswald, den 18. Juli 1903. 



Nachdruck verboten. 



The Embryology of Tumours *). 



By J. Beakd, D. Sc, 

 University Lecturer in Comparative Embryology, Edinburgh. 



The subject-matter treats of the etiology of cancer and other 

 tumours, and contains suggestions as to a line of research to be 

 taken up for the discovery of a cure for cancer. Tumours are shown 

 to be referable to 1) abnormal attempts at development on the part 

 of one or more vagrant or aberrant primary germ-cells, and 2) the 

 bizarre pathological manifestation by such of some greater or less 

 portion of the life-cycle of normal development. Following Cohnheim, 

 many, but not all, pathologists have attempted to explain tumours or 

 neoplasms by the hypothesis of rests of embryonic organs, which, 

 lying unused and dormant in the development, might at a later period, 

 suddenly awaking into activity, give rise to an abnormal growth, a 

 tumour. Other pathologists set down the tumours as due to "meta- 

 plasy" (Virchow), that is to say, to a change in the characters of 

 cells or tissues at some early or later period of life. Thus, it has 

 been supposed, that ordinary cells of fibrous connective tissue can 

 alter their nature and give rise pathologically to cartilage or bone. 

 The foregoing views are purely hypothetical; they have no basis 

 whatever in the facts of embryology, and in nature, as we know it, 

 they are impossibilities. 



Tumours in general, from the highest, the teratomata or rudi- 

 mentary embryos (embryomata of Wilms), to sarcoma and cancer itself, 



1) Abstract of a paper read before the Royal Society, Edinburgh^ 



on Eebr. 16th, 1903. 



