THE GENERAL CONSTITUTION OF LIVING BEINGS. 79 



mother. The materials that have acted together in the 

 gradual production of these elements have come to it only 

 molecule by molecule, through the enveloping membranes. 



Robin's doctrine with regard to the production of 

 anatomical elements within blastemas is not accepted by 

 some German physicians, who persist in maintaining the 

 cellular theory ', established in vegetable physiology about 

 1838 by Schleiden, and extended later by Schwann to ani- 

 mal physiology. This theory admits that all the anatomi- 

 cal elements of animals proceed from a succession of direct 

 transformations of the cell. One single primordial cell is 

 the source of the most dissimilar elements, nerve-elements, 

 muscle-elements, etc. The cell springs from the cell by 

 proliferation / the other elements spring from it by meta- 

 morphosis. The most complex organism thus results, 

 through a series of varied transfigurations, from one simple 

 rudimentary ovule. It is, as we see, the doctrine of Lamarck 

 and of Darwin, applied to the genesis of the embryo. The 

 question is important. It has lately given rise to cele- 

 brated discussions, and perhaps it is as well to consider 

 it briefly here. 



Omnis eellula e eellula, say the partisans of Schwann's 

 theory. That might be readily granted, if the system con- 

 tained none but similar cells ; but there is in it a great 

 number of elements so distinct that the mind cannot com- 

 prehend how some of them could be emitted by the rest. 

 It refuses to allow, for instance, that leucocytes, which 

 water attacks and acetic acid dissolves, proceed, by pro- 

 liferation, either from neuclei of cellular tissue or from 

 epithelial nuclei, which those reagents do not affect. We 

 can hardly believe that sons are so very unlike their fathers. 

 We can form no idea how muscular fibres and nerve-tubes 

 can issue from globules that bear no resemblance whatever 

 to them, either as regards composition or as regards proper- 

 ties. Besides, such a relationship has never been directly 



