PROTOPLASM AS A PHYSICAL SYSTEM 59 



in mechanical and chemical properties already described. 

 On such a view the cytolytic action of lipoid-alterant 

 compounds may be explained. Such compounds act 

 by destroying the film-structure; hence, in addition to 

 destruction of semi-permeability, they break down the 

 intracellular, partitions and induce chemical reactions of 

 the above-described kind and cause coagulation of the 

 cell-proteins. In irritable cells such compounds have 

 also a strongly stimulating action of an irreversible kind, 

 as shown in the contraction produced in muscle cells, 

 and similar effects. 



The above-described loss of translucency accompany- 

 ing cytolytic or mortiferous processes is a phenomenon of 

 much interest, which has an intimate bearing on the 

 general problem of protoplasmic structure. This change 

 is shown with great clearness in all of the more transpar- 

 ent forms of protoplasm; e.g., the eggs of marine animals 

 (starfish, etc.), protozoa, and muscle cells. Some years 

 ago while studying the conditions of activity in the cteno- 

 phore swimming plate — a beautiful example of a clear 

 translucent protoplasm, consisting of parallel contractile 

 fibrils (fused ciha) — I was struck with the constancy and 

 definiteness of the relations existing between changes of 

 translucency and changes of contractile activity. In 

 dying animals the plates become partially clouded and 

 adopt a rapid unintermittent movement, differing from 

 the normal movement in being of quicker rhythm and in 

 no longer showing the mechanical inhibition described 

 above; this movement continues until finally the plate 

 becomes white and opaque and all activity ceases.^ 



'R. S, Lillie, American Journal of Physiology, XVI (1906), 117; 

 XXI (1908), 200. 



