Chapter III — 9 — Physical Properties 



Viscosity:- There has been a good deal of discussion concerning 

 the cohesive state of cytoplasm, i.e., its consistency. Most cytolo- 

 gists consider that the cytoplasm more nearly approaches a liquid 

 than a solid state. A few, however, believe it to be of a solid 

 consistency. 



The Plasmodium of the Myxomycetes is very fluid. A proof of 

 this is in an experiment carried out on Badhamia utricularis by 

 the English mycologist, Lister. Lister noticed Plasmodia of this 

 fungus on the trunk of an old hornbeam growing in his garden. 

 The trunk was covered over with the fruiting bodies of Corticium 

 puteanum. The Plasmodia of Badhamia moved around on the sur- 

 face occupied by Corticium, actually consuming the fruiting bodies 

 and after their passage leaving the bark of the hornbeam as smooth 

 and clean as if no fungus had ever grown there. But, although 

 Badhamia assimilated the Corticium tissues, its spores, protected by 

 a resistant brown membrane, were not attacked and accumulated 

 within the Plasmodium which 

 took on a dark brown color. Lis- 

 ter collected one of these Plas- 

 modia on a glass plate, where it 

 moved about, leaving behind it as 

 evidence of its passage, a fine 

 brown network, formed of the 

 ingested spores. These had been 

 progressively dropped, being 

 poorly retained in the plasmodial 

 cytoplasm. This demonstrates 



its weak viscosity. The plasmo- 



dium, however, still enclosed fig. 4. - Two successive shapes, a. b, 



many spores. Lister then put in ^^^^^ ^y the Plasmodium of a Myxomycete 



•1 ,1 1 . « , ■ . as it moves in the direction of the arrow. 



Its path a barrier of wet cotton. 



The Plasmodium passed through rapidly, leaving in the cotton all the 

 remaining spores, and emerged showing the yellow tint characteris- 

 tic of it before it had taken up the fungus Corticium. Lister thus 

 brought about the filtration through cotton of plasmodial protoplasm 

 and in this way succeeded in demonstrating its very fluid consistency. 

 This somewhat crude evidence may be made more specific by 

 a detailed examination of the Plasmodium. It is composed of a 

 network of opaque, anastomosing veins which, in certain species, 

 may attain large dimensions: even a diameter of several milli- 

 meters in the case of the principal veins. Toward one border, the 

 network merges with a fan-shaped continuous layer of the same 

 material. This entire body moves at about the rate of 1 cm. per 

 hour and presents constantly changing contours ; nevertheless the 

 continuous layer is always in front and may be interpreted as 

 protoplasm flowing slowly over the substratum. The substance 

 composing the Plasmodium is, in fact, fluid and motile but shows at 

 its surface the ability to coagulate. A puncture in a vein allows 

 a drop of the internal fluid protoplasm to escape. This drop is 

 immediately coagulated on the surface. The internal protoplasm, 



