202 PROTOPLASM 



in early times, occupied themselves with the study of the 

 living object, in order to ascertain the existence of structures 

 in living protoplasm. Since, moreover, the living nuclei 

 frequently showed still more distinct structures of a similar 

 kind, it seemed all the more justiiiable to regard the exist- 

 ence of the protoplasmic structures during life also as a 

 certain fact. 



As is well known, some later observers, as more especially 

 Berthold, Fr. Schwarz, and, in connection with the latter, 

 also Kolliker, have disputed the idea that reticular structures 

 are present in living protoplasm. In their opinion they are 

 artificial products, so far as they do not depend upon patho- 

 logical vacuolisation, i.e. appearances artificially produced by 

 precipitation or coagulation of the protoplasm. Berthold, 

 who first expressed this view in 1886, has come forward 

 again, as is well known, with good arguments, and in a very 

 praiseworthy manner, to vindicate the fluid nature of pro- 

 toplasm, which was taken for granted almost universally at 

 an earlier period. It possesses, according to him, the char- 

 acter of an emulsion, i.e. it is a mixture of two or more 

 fluids which are insoluble in one another, or only soluble to 

 a limited extent. Of course it was also quite in accordance 

 with his view for solid secretions in the form of granules or 

 crystals to appear in the protoplasm. Berthold seeks very 

 correctly to refer the emulsive character of protoplasm to 

 the so-caUed processes of desolution, which have already been 

 briefly explained above, and were found to be the true 

 efficient cause of the formation of oil-foams. When Ber- 

 thold terms his conception of protoplasm, and, more particu- 

 larly, his statements as to its fluid nature, a hypothesis 

 merely, I think he is too sceptical in this respect. I shall 

 try to explain later on, as I have already done before, that 

 the fluid nature of more ordinary protoplasm follows very 

 definitely on the contrary from all the phenomena observed. 

 It will then also be discussed how the view gradually 

 developed that protoplasm could not be fluid, or that it 

 must at least be a mixture of solid and fluid parts. If 

 then Berthold, by reason of his view of the fluid and emul- 

 sive nature of protoplasm, got so far as to deny a reticular 



