36 ON THE PLANT-CELL. 



these cells are formed in the same way as those of plants. Tf this law is 

 found essential to some plants and animals, this analogy forms a basis for 

 enunciating this mode of formation as a universal law for both kingdoms 

 of nature. 



In the same work Schwann has given an interesting comparison be- 

 tween the formation of crystals and cells, and he was led to this from a 

 consideration of the nature of the substances of which the last are formed. 

 This view in future may be of the greatest importance, as it shows that 

 the apparent gulph between the organic and inorganic kingdoms may not 

 be impassable. There is one point to which I would allude, and which 

 seems to have escaped the attention of Schwann. In the formation of 

 the crystal, the matter of the same already exists, as such, dissolved in the 

 fluid, and only awaits the withdrawal of the solvent to assume its peculiar 

 form : it is otherwise in the cell of the plant. Here the organic substance 

 forming the substance of the cell is not present in the cytoblast, but is 

 formed through another necessarily present substance, and this only takes 

 place when the new-formed substance is relatively insoluble. 



In the crystallisation of salts, such as the nitrate of potassa, from a 

 solution, we can observe the increase of the crystal from additions to it 

 from without. But, on the other hand, if we take a solution of two sub- 

 stances which form, when mixed, a precipitate, we shall find, on examining 

 this under the microscope, that a membrane divides the two fluids. Ac- 

 curate observation will show that this membrane consists of crystals of 

 various sizes. If the fluid remains quiet, some of the crystals are projected 

 into it on both sides ; if the fluids are mixed, the crystals are dissolved up 

 again. After many careful observations, I believe that all inorganic sub- 

 stances, if they are allowed to remain quiet, assume a crystalline form; 

 and that the so-called pulverulent precipitates consist of crystals, the form 

 of which, from their smallness, cannot be observed. 



In the last place I must mention a highly interesting analogy, which, 

 when more accurately examined, may perhaps one day lead to the most 

 satisfactory explanation of the process of cell-formati on, I mean vinous 

 fermentation. We have here a fluid in which sugar and dextrin, and a 

 nitrogenous matter, as a cytoblast, are present. At a certain temperature, 

 which is perhaps necessary to the chemical activity of the mucus, there 

 originates, without, as it appears, the influence of a living plant, a process 

 of cell-formation (the origin of the so-called fermentation -fungus), and it 

 appears that it is only the vegetation of these cells which produces the 

 peculiar changes that occur in the fluid. Whether this organism is really 

 a fungus, is a matter of indifference; but whether it alone, through the 

 activity of its vital processes, determines the process of fermentation, 

 deserves to be accurately determined. 



I will here add my own observations on these fermentation-cells. I 

 bruised some currants with sugar, and, having pressed the juice through 

 a cloth, diluted it with water and filtered through folded paper. The fluid 

 was bright red, quite clear and transparent, and, under the microscope, 

 showed no trace of granules, but presented a number of little drops of a 

 pure clear oil. At the end of twenty-four hours the whole fluid was 

 opalescent, and presented, under the microscope, a number of granules 

 suspended in it (fig. 9. #, Plate I.). On the second day these granules had 

 greatly increased, and there appeared amongst them perfectly-formed 

 ferment-cells (Plate I. fig. 9. a, b, c). There also appeared, now and then, 



fibres (Henle, General Anatomy), have no analogues in plants. [Schwann's treatise 

 lias been translated and published by the Sydenham Society. TRANS.] 



