378 PROF. TH. W. ENGELMANN. 



For our knowledge of the chemical composition of pure pro- 

 toplasm we are really dependent upon its micro-chemical 

 reactions. On this account our existing knowledge in this 

 respect is extremely scanty. It must be specially noted that 

 there is no chemical mark by which contractile can be sepa- 

 rated from non-contractile protoplasm. 



In life the reaction of protoplasm is generally weakly alka- 

 line or neutral;^ in ^thalium septicum it is always dis- 

 tinctly alkaline. 2 Now and then I have seen blue litmus 

 particles change within a few minutes after being taken into the 

 contractile endoplasm of Stylonychia mytilus and S. pus- 

 tuluta, Paramcecium aurelia, and Amoeba diffluens, 

 to a red colour and remain so.^ 



Among the solid substances which often make up together 

 10 — 20 per cent, of the total weight, albuminous granules 

 make up by far the greater mass, as is usual in protoplasm. 

 And, indeed, albuminous granules are always observable, at 

 any rate at a lower temperature than that at which they 

 coagulate (generally under 50°). In addition to these, car- 

 bohydrates (in the plasmodium of ^Ethalium there is a 

 quantity of glycogenous substance*), fat, inorganic substances, 

 especially potash compounds, are seldom absent. Lecithin is 

 also frequently present. In the plasmodium of -^thalium 

 septicum a peptic enzym is found. ^ 



* Th. W. Eagelmann, " Ueber die Flimmerbewegung," ' Jenaisciie Zeitsch. 

 f. Med. u. Naturw.,' iv, p. 469, Anm., 1868. 



2 ' Briefll. Mittheil.,' von De Bary ; C. W. F. Krukenberg, ' Unters. d. 

 physiol. Instit. d. Univ./ Heidelberg, ii, p. 273, 1878. 



^ This is possibly due to an acid secreted in an attempt, to digest the particles. 

 I have observed Vorticellai in a watery solution of aniline blue taking it in 

 rapidly and becoming filled with blue vacuoles, the contents of which are 

 gradually absorbed, the blue colouring matter reappearing of a different tint in 

 the contractile (excretory) vacuole. — Transr. 



< ' Briefl. Mittheil.,' von W. Kuhne. 



* Krukenberg and others. 



