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Prof. Rudolf Virchow. The Position of [Mar. 16, 



searches very soon encountered great difficulties. Many tissues, even 

 in their developed state, appeared to contain neither cells nor their 

 equivalents ; nevertheless, I have been able to demonstrate their 

 existence in those tissues in which their presence appeared to be 

 most doubtful, viz., in bone and connective tissues. At the present 

 time we are so far advanced as to be able to say that every living 

 tissue contains cellular elements. We go a step further even, for we 

 require that no tissue should be called living in which the constant 

 occurrence of cells cannot be shown. 



A still greater difficulty then appeared, namely, to discover in 

 what way new cells originated. The answer to this question had been 

 very heavily prejudiced by the so-called cell-theory of Schwann. 

 Inasmuch as this very trustworthy investigator asserted that new 

 cells originated from unformed matter, from " cyto-blastema," 

 there was opened up a wide road to the old doctrine of the " generatio 

 sequivoca," which afforded all partisans of plastic materials an easy 

 way of reviving their dogma. The discovery of cells of connective 

 and allied tissues gave me the first possibility of finding a cellular 

 matrix for many new growths. One observation followed another, 

 and I was soon in a position to give utterance to the dictum, " Omnis 

 cellula a cellula." 



And so at last the great gap was closed which Harvey's ovistic 

 theory had left in the history of new growth, or, to speak more 

 generally, in the history of animal organisation. The begetting 

 of a new cell from a previous cell supplements the reproduction of one 

 individual from another, of the child from the mother. The law of 

 the continuity of animal development is therefore identical with the 

 law of heredity, and this I now was able to apply to the whole field 

 of pathological new formation. I blocked for ever the last loophole 

 of the opponents, the doctrine of specific pathological cells, by show- 

 ng that even diseased life produced no cells for which types and 

 ancestors were not forthcoming in normal life. 



These are the fundamental principles of cellular pathology. 

 In proportion as they have become more certain, and more generally 

 recognised, they have in turn become the basis of physiological 

 thought. The cell is not only the seat and vehicle of disease, but also 

 the seat and carrier of individual life ; in it resides the " vita propria." 

 It possesses the property of irritability, and the changes in its sub- 

 stance, provided these do not destroy life, produce local disease. 



Disease pre- supposes life ; should the cell die, its disease also comes 

 to an end. Certainly, as a consequence, the neighbouring and even 

 far-distant cells may become diseased, but as regards the cell itself 

 the susceptibility to disease is extinguished with life. 



Since the cellular constitution of plants and animals has been 

 proved, and since cells have become recognised as the essentially 



