234 PROTOPLASM 



(c) External Surface of the Protoplasm 



Considerations quite similar to those which we have put 

 forward with regard to the vacuoles also hold good for the 

 external surface of the protoplasmic body. Consistent 

 adherents of the framework theory, such as Ley dig (1883 

 and 1885) in particular, did not shrink from the assumption 

 that the outer surface of protoplasm, the surface of the cell 

 in general, was not formed of a continuous layer of substance, 

 but that it was " porous," in keeping with the spongy 

 structure of the protoplasm. Thus Ley dig says (1885, p. 

 15) the outer surface of the cell is always porous, " inasmuch 

 as it consists of a meshed framework and an intervening 

 matrix enclosed by it." Even in 1883 he asserted the 

 same thing. In this respect his interpretation of the thin 

 stratum of alveoli, forming a single layer only in the cells 

 of the capillaries, appears characteristic, since he explained 

 them as porous (see above, p. 144). This strange conception 

 of Leydig's is, moreover, intimately connected with his view 

 of the importance of the intervening matrix as the true 

 living substance of the protoplasm, according to which, in 

 fact, the intervening substance was supposed to creep out of 

 the framework in the form of the pseudopodia. For this 

 purpose it was of course necessary that the surface should 

 not be covered by a continuous layer of the framework. 



Frommann also was constrained to put forward similar views 

 for naked protoplasm. Thus he remarks (1880), with regard to 



parently conceives of as a fluid which permeates the protoplasm evenly and 

 continuously, is open to an essentially different interpretation on the ground 

 of my investigations. This imbibition fluid is in reality the enchylema 

 contained in the alveoli, and since it is always shut off by very fine lamella? 

 of protoplasm, the conditions of osmosis are always present even when the 

 external protoplasmic membrane does not exist or does not possess the sig- 

 nificance ascribed to it. If one supposes, however, with Pfeffer, that this 

 imbibition fluid is one permeating the protoplasm continuously, it must of 

 course be assumed that a special protoplasmic membrane exists at the 

 surface, which controls the osmosis of the imbibition fluid. As has been 

 said, however, I do not regard this assumption as inevitable, but it seems 

 to me that the protoplasm as such, i.e. the lamella? of the alveolar framework, 

 suffice for the explanation of the osmotic processes. 



