70 MOllBID GROWTH IX GENERAL. 



Ill tliis pure fluid minute granules were first of all developed ; 

 these united to form nucleoli, then nuclei, and last of all cells. 

 As time wore on, men grew more cautious ; the possibility of 

 cell-formation was made conditional ofi the presence of at least 

 the elementary granules pre-formed in the blastema. 



It cannot be denied that a transition period of mixed theories 

 intervened between the original doctrine and that finally estab- 

 lished by Virchow : oiimis cellula e celluld. Wherever cells are 

 present in the organism they are the progeny of other cells 

 which have ceased to exist ; they inherit the existence, though 

 not always the peculiarities and vital properties, of their pro- 

 genitors. The question as to the mode in which cells originate 

 was thus permanently settled. Tlie cells which we find among 

 the products of morbid growth likewise owe their origin to the 

 division of pre-existing cells. But of what pre-existing cells ? 

 This still demands an answer. VirchoiCj whose authoi'ity on this 

 subject has been absolute during a'period of ten years, elaborated 

 the theory that the cells situated at the point occupied by the 

 growth undergo multiplication by fission, that the new tissues 

 were actually substituted for a certain proportion of the normal 

 constituents of the body. On the other hand, Cohnheiin has 

 established beyond all doubt that a migration of colourless cor- 

 puscles from the vessels — a plastic exudation in the strictest 

 sense of the word — may supply the materials for morbid growth. 

 Of course, these corpuscles also result from the proliferation of pre- 

 existino; cells ; but the parent-cells are at a distance from the seat of 

 disease; they are in the blood, the spleen, the lymphatic glands. 

 This, indeed, does not exclude the possibility of growth taking 

 place in loco morhi; on the contrary, Strieker's recent researches on 

 inflammation afford conclusive evidence that migration is followed 

 by fission of the emigrant cells, and, within certain limits, of 

 those cells also which exist pre-formed at the seat of mischief. 



^ ^Q, Led away by these inquiries into the fundamental 

 nature of the process, observers have in the meantime neglected 

 to institute a more careful comparison of morbid with normal 

 growth. I will endeavour, to the best of my ability, to remedy 

 this defect ; but some preliminaries of a general kind must first 

 be settled. And, in the first place, we must not rest content with 

 the bare assertion that cells originate from cells, without being at 

 the pains of acquiring a fuller knowledge of the minuter details 

 of the pi'ocess. The cells of the adult organism differ very 



