30 Chapter II 



composition of the " humours " in the two kingdoms, the cell-juice of 

 plants being generally acid ; under this condition the Fungi develop 

 much better than do the Bacteria. 



The various modes of defence against infective diseases that have 

 been met with in unicellular organisms are also found in the multi- 

 cellular plants. Whereas in almost all plants the cells are rigid, 

 owing to the presence of a well-developed membrane, some of the 

 lower plants have preserved a condition in which the protoplasm is 

 completely naked and capable of movement. Myxomycetes are 

 specially distinguished by an amoeboid stage of existence and by the 

 formation of large plasmodia which protrude protoplasmic processes 

 and exhibit a kind of locomotion similar to that met with in the 

 Rhizopods and the Sporozoa. 



Infective diseases among the Myxomycetes must be very rare 

 since, up to the present, they have not been noted by a single observer. 

 It is very probable that the plasmodia get rid of the infective germs, 

 as do the Protozoa, both by expulsion of the parasites and by 

 means of intracellular digestion. This latter takes place in a medium 

 which is distinctly acid and by means of a soluble ferment described 

 by Krukenberg 1 as a kind of pepsin. I need not here enter into 

 further detail as I have already treated this subject in my Lectures 

 on the comparative pathology of inflammation. The fact that the 

 Myxomycetes can ingest living organisms has been demonstrated by 

 Celakovsky, jun. a , who has observed that the spores of the various 

 Fungi can germinate in the interior of the plasmodium. Whilst our 

 conceptions concerning the resistance of the plasmodia in regard to 

 micro-organisms are merely based upon analogies and hypotheses, our 

 ideas as to their immunity against soluble substances rest on well- 

 established experimental facts. We owe to Stahl 3 our first informa- 

 tion as to the mode by which the plasmodia resist poisons. When 

 they are placed in contact with solutions of salts, of acids or of sugar 

 in a sufficiently concentrated form to bring about an injurious action, 

 the plasmodia make use of their amoeboid power of motion to escape 

 [ssjfrom these fluids. Hence they exhibit a negative chemiotaxis, ex- 

 actly parallel to that so often observed in the case of the unicellular 

 organisms. Consequently there is in the Myxomycetes a natural 

 immunity due to the activity of their movements. Further, a kind 



1 Untersuch. a. d. physiolog. Inst. d. Univ. Heidelberg, 1878, Bd. n, S. 273. 



2 Flora, Marburg, 1892, Bd. LXXVI, S. 182. 



3 Boian. Ztg., Leipzig, 1884, S. 161. 



