THE BEGINNINGS OF LIFE. 23 I 



this, though a mode of origin of new organic units 

 which has been long spoken of by Dr. Beale, is not 

 one which has been much mentioned by Virchow and 

 others of the Cellular School of Pathology. They speak 

 principally of cell multiplication taking place by equal 

 division of pre-existing cells or nuclei a mode of 

 reproduction which, though undoubtedly very common, 

 does not, in my opinion, play such an important and 

 almost exclusive part in tissue growth as has been 

 represented, and which does not, moreover, enable us 

 to account for many appearances that are frequently 

 met with. 



Cells may also originate after another fashion in the 

 human body, as I have satisfied myself from a most 

 careful study of the results of inflammation when 

 occurring on the pericardium, or lining membrane of 

 the heart. It appears that small nuclei-like bodies, or 

 plastides, about 45 1 00 " in diameter originate by a direct 

 process of differentiation, from the homogeneous and 

 tenacious so-called c lymph' which is produced on the 

 surface of the serous membrane 1 . This structureless 

 lymph-like matter is capable of being resolved, or of 

 differentiating, more or less rapidly, into an areolar 

 tissue and plastides of the kind above mentioned. I 



1 In what precise way this is produced we have still no certain 

 knowledge. I feel convinced that it is no mere 'exudation' from the 

 blood-vessels ; neither is it produced by an abundant proliferation and 

 over-growth of the superficial tissue elements. It is at first quite struc- 

 tureless, and, judging from the changes which it subsequently undergoes, 

 it seems to be formless living matter. 



