34 GENERAL ANATOMY OF THE TISSUES. 



the development of Ascherson's vesicles. Which of these 

 various possibilities really obtains, must at present remain unde- 

 termined, yet, for my own part, I should prefer the first view, 

 in order to retain one and the same condition, a physical one, 

 for all the different modes of cell-development. 



I do not think it necessary to enter at greater length, in 

 the present place, into this very obscure subject, and I will 

 therefore only once more express my opinion, that I hold the 

 physical processes in cell-development, which may pass under 

 the general name of molecular attraction, to be something quite 

 different from those which attend crystallisation. Although in 

 both, solids arise out of fluids, and grow by the further agglo- 

 meration of molecules, yet in cell-development different sub- 

 stances are as a rule superimposed, plane geometrical solids are 

 never formed, and the process is always limited in the same way, 

 after the formation of the cell-membrane. Since organic and 

 even histogenetic substances are crystallisable, the reason of 

 cell-development is not to be found in permeability nor in any 

 of the other properties of organic compounds, which in fact, 

 even if these substances did not crystallise, would not suffice to 

 explain all the peculiarities of cells in question, nor their power 

 of self-division and multiplication ; but in those peculiar, as yet 

 unknown combinations of the powers of nature which are con- 

 cerned in organic development. To discover these is the further 

 and difficult task of Histology, which to this end must be 

 wholly directed to the so-called molecular forces of organic 

 forms, especially to those electrical phenomena which must 

 indubitably occur in the cells as well as in their derivative 

 structures, the nerve-tubes and muscular fibres. 1 



1 [The essential distinction between living organised matter (the cell) and mere 

 inorganic formed matter (the crystal) appears to us to be here overlooked. If some 

 inorganic substance should be discovered crystallising in the form of nucleated cells, 

 it would not the more approximate to an animal or vegetable cell ; for the essential 

 character of the latter, which is its passage through a definite succession of states and 

 not its form merely, would still be absent. It is this characteristic peculiarity of 

 organised living beings, which has been exhibited with so much force by Alex. Braun, 

 in the plant, under the somewhat fanciful title of ' Verjiingung' (rejuvenescence), 

 but which equally obtains in the animal. The crystal tends to attain a permanent 

 condition, the cell towards its own disappearance, either by death or division. 

 The crystal tends towards an equilibrium with the forces around it, the cell inces- 

 santly disturbs that equilibrium, — life and change being one. — Eds.] 



