10 THE GENERAL CHARACTERS OF CELLS, BY S. STRICKER. 



nomena which are characteristic of an independent animal 

 an independent organism. 



PHYSIOLOGICAL PECULIARITIES OF CELLS. Contractile sub- 

 stance, or protoplasm, appears, when examined with the best 

 microscopes, to be homogeneous, or destitute of structure. It 

 rarely occurs, however, in a pure state; for small particles are 

 usually imbedded in it, which have either been taken up from 

 without, or have formed in the interior as a consequence of 

 chemical processes. If the protoplasm contain many coloured 

 corpuscles, the cell is termed a pigment cell ; if it contain fat 

 molecules, a fat or granule cell. The presence of small colour- 

 less, dull, or shining granules is indicated by the term granular 

 applied to the cell, and of such cells two kinds are distinguished 

 those that are coarsely and those that are finely granular. 



When other kinds of material are contained in the cell, their 

 presence is indicated by appropriate terms. It is thus usual to 

 speak of starch-holding cells, and the like. 



Since the researches of Hackel (see p. 16) have shown us that 

 foreign matters can penetrate into the interior of the protoplasm, the 

 origin of all such particles must be investigated. We must determine 

 in every case whether a body which lies in the interior of the cell is 

 the result of some chemical process in the interior of the protoplasm, 

 or has been introduced from without. If particles of colouring matter 

 are artificially caused to enter, as has been successfully accomplished by 

 Eecklinghausen, Max Schultze, Billroth, Cohnheim, and others ; then 

 the question as to whence the colouring matter proceeds is answered by 

 the experiment itself. But it is more difficult to decide from whence 

 those bodies that are found imbedded in cells proceed, which occur with- 

 out the agency of the experimenter. The determination of this point 

 may prove, however, of extraordinary importance. Since, for example, 

 Preyer showed that portions of red corpuscles are eaten by the amoe- 

 boid cells of the frog, we could not admit without much proof that 

 the presence of red corpuscles in the interior of the white was due 

 to the development of the former in the interior of the latter. 



* " 



The consistence of protoplasm varies within moderately 

 wide limits. It may, like a fluid, form drops, assuming, when 

 in small quantities, a spherical form, or may extend itself upon 



