444 



SCIENTIFIC THOUGHT. 



44. 



The proto- 

 plasmic 

 theory. 



and the year 1863 is usually given as that in which 

 the protoplasmic theory was established. According to 

 this view protoplasm is the element or unit of all living 

 substance : it grows through assimilation (intussusception 

 and excretion), and multiplies (i.e., gives rise to other 

 living units) by subsequent division. This process was 

 found to be fundamental : it describes the growth of 

 the simplest and the most complicated organisms as 

 beginning alike with a unit cell, which may or may 

 not grow by division ; it is the formula of growth, 

 restitution, and generation (whether sexual or asexual) ; 

 and, what is equally important, it prevails also in patho- 

 logical cases i.e., in the formation of diseased tissues. 

 In fact, the great generalisation which followed Harvey's 

 celebrated dictum, " omne vivum ex ovo," was put forth 

 by the late Professor Rudolf Virchow, the eminent 

 founder of cellular pathology, in his formula, " omnis 

 cellula e cellula." The formula has in more recent 

 times been further elaborated on the same lines of 

 thought in proportion as the importance of the nucleus 

 or cell kernel has been recognised, or as the granular 

 structure of protoplasm has been maintained; leading 

 to analogous formulae, such as " omnis nucleus e nucleo," 

 " omne granulum e granulo." These formulae 1 are the 



1 See Roux ('Gesammelte Ab- 

 handlungen,' vol. i. p. 393) : " Un- 

 interrupted durability is the in- 

 dispensable condition of all that is 

 organic, although this does not 

 involve a distinction from inorganic 

 processes. This fact is expressed 

 by the fundamental theses : Omne 

 vivum ex ovo (Harvey), Omnis 

 cellula e cellula (Virchow), Omnis 

 nucleus e nucleo (Flemming)." 



Hauptmann ('Die Metaphysik,' 

 &c., p. 334) says : " Altmann for- 

 mulates for himself in analogy 

 with these biological principles the 

 further principle, ' Omne granulum 

 e granulo. ' " On Altmann's theory 

 of the ' ' bioblasts " as elementary 

 organisms, see Yves Delage, 

 ' L'Herddite,' p. 498, &c., Hertwig, 

 'The Cell,' p. 24. 



