40 MORPHOLOGY OF THE CELL. 



and mechanical processes ; the reactions of livhig protoplasm towards chemical reagents 

 are essentially different from those of dead protoplasm, but this of course can only 

 be perceived when the reagents do not at the same moment cause death. Solutions 

 of different colouring matters, as aqueous solutions of the colours of flowers and the 

 juices of fruits, especially also weak acetic extract of cochineal, have no power of colour- 

 ing living protoplasm^; but if it has previously been killed, or if it has been deprived of 

 its life-giving condition by continual action of these reagents, it absorbs a proportionately 

 larger quantity of colouring material as a solvent ; the whole substance assumes a much 

 more intense colour than the solution itself. Solutions of iodine in water, alcohol, potas- 

 sium iodide and glycerine, act in a similar manner; they all cause a yellow or brown 

 colouring of the protoplasm, which is more intense than that of the solution itself. If 

 protoplasm is first heated with nitric acid, the excess of acid removed by water, and 

 solution of potash added, it assumes a deep yellow colour ; saturated with a solution of 

 copper-sulphate and then treated with potash, it becomes of a beautiful dark violet. 

 Protoplasm containing but little water treated with a large quantity of concentrated 

 English sulphuric acid, assumes a beautiful rose-red colour, without at first changing its 

 form ; subsequently this colour and the form disappear together, the protoplasm dissolv- 

 ing. Dilute solution of potash (sometimes also liquid ammonia), dissolves protoplasm, or at 

 least destroys its form, and makes it homogeneously transparent. If, on the other hand, 

 cells with protoplasm of characteristic form are placed in a concentrated solution of 

 potash, the form itself remains for weeks, but disappears immediately on addition of 

 water. All these reactions are collectively characteristic of true albuminoids, as caseine, 

 fibrine, albumen ; and we are therefore justified in supposing that substances of this kind 

 are always contained in protoplasm. If the protoplasm-sac in cells rich in sap is very 

 thin, it acquires a greater power of resistance, and withstands the solvents mentioned 

 for a longer or shorter time. In another respect also protoplasm behaves like albumin- 

 oids ; by heating very watery protoplasm to above 50° G. it is killed, and becomes turbid 

 and stiff, and gives the impression of coagulation ; alcohol and dilute mineral acids act 

 in the same manner. The nucleus behaves towards all colouring substances, solvents, 

 and coagulating agents in the same manner as living watery protoplasm, or it shows itself 

 even more sensitive, especially in young cells ; in older cells however it may be less easily 

 acted on. 



At the base of all protoplasmic structures there probably lies a substance which 

 is colourless, homogeneous, and not visibly granular, to it alone the name Protoplasm 

 ought perhaps to be applied, or at all events it ought to be distinguished as the founda- 

 tion of protoplasm. The fine granules which are so often mingled with it, and which 

 some used to consider an essential ingredient, are probably finely divided assimilated 

 food-materials, which undergo a further chemical metamorphosis into protoplasm ; every 

 intermediate form occurs from these more or less fine granules to the largest, which may 

 be clearly recognised as fat and starch. Homogeneous protoplasm destitute of granules 

 is found in the cotyledons of dormant embryos of Helianthus, and in the cotyledon- 

 leaves of Phaseolus ; out of it chlorophyll is subsequently formed, and here the proto- 

 plasm contains but very little water ; but the extremely watery protoplasm which rotates 

 in the cells of Vallisneria is also destitute of granules ; nothing but nucleus and grains 

 of chlorophyll can be recognised in it. In the development of the spores of Equisetum 

 (Fig. 10) the finer granules separate repeatedly from the homogeneous protoplasm, and 

 afterwards become again distributed through it. But in some cases the protoplasm is so 

 loaded with granular and coloured materials, that the colourless hyaline original sub- 

 stance can no longer be distinguished, as, for instance, in the ova of Fucus (Fig. 2), 



^ In tlie same manner the protoplasm and nucleus in living cells with coloured sap are also 

 colourless; in other cases, on the other hand, the protoplasm is tinged by a colouring matter 

 soluble in water, which is not present in the cell- sap. (As in Floridecc and the flowers of Com- 

 positoe, the last accordinc; to Askenasy.) 



