CELLS AS VITAL UNITS 191 



from this point of view the embryo can be compared up to 

 a certain point with a zoophyte stock, of which each polyp, 

 while living its own independent life, is yet incorporated in 

 the common corm, which impresses its distinctive character 

 upon every polyp " (p. 293). 



Classical expression was given to the " colonial theory " 

 of the organism by Virchow in his lectures on " Cellular 

 Pathology." 1 For Virchow the organism resolves itself into 

 an assemblage of living centres, the cells ; the organism has 

 no real existence as a unity, for there is no one single centre 

 from which its activities are ruled. Even the nervous system, 

 which appears to act as a co-ordinating centre, is itself an 

 aggregate of discrete cells. " A tree is a body of definite 

 and orderly composition, the ultimate elements of which, 

 in every part of it, in leaf and root, in stem and flower, 

 are cellular elements so also are animal forms. Every 

 animal is a sum of vital units, each of which possesses the full 

 characteristics of life. The character and the unity of life 

 cannot be found in one definite point of a higher organisation, 

 for example in the brain of man, but only in the definite, 

 constantly recurring disposition shown individually by each 

 single element. It follows that the composition of the 

 major organism, the so-called individual, must be likened to 

 a kind of social arrangement or society, in which a number 

 of separate existences are dependent upon one another, in 

 such a way, however, that each element possesses its own 

 particular activity, and, although receiving the stimulus to 

 activity from the other elements, carries out its own task 

 by its own powers" (2nd ed., pp. 12-13). 



Analysis, decomposition, or disintegration of the organism 

 is here pushed to its extreme point, and the problem of 

 recomposition, synthesis and co-ordination shirked or for- 

 gotten. 



The harmful influence of the cell-theory upon morphology 

 did not pass unnoticed by the broader-minded zoologists of 

 the day. Virchow's earlier paper 2 on the application of the 



1 Die Celhilarpathologie in ihrer Begriindung aiif physiologische tend 

 pathologische Gcwebelchre, Berlin, 2nd ed. 1859 ; Eng. trans., by Chance, 

 1860. 



- Arch. path. Anat. Phys., vii., pp. 1-39 (1854). 



