EXPERIMENTS ON THE PHYSICAL STUCTURE OF 

 THE PROTOPLASM OF PARAMCECIUM AND ITS 

 RELATION TO THE REACTIONS OF THE ORGAN- 

 ISM TO THERMAL, CHEMICAL AND ELECTRICAL 

 STIMULI. 



ARTHUR W. GREELEY. 



CONTENTS. 



PAGE. 



Introduction 3 



Structural Reactions of the Protoplasm of Protozoa to Physical and Chemical 

 Changes. 



I. Reactions to Variations in the Temperature 8 



II. Reactions to Chemical Changes 9 



III. Reactions to the Electrical Current 19 



Effect of these Structural Modifications on the Vital Properties of the Protoplasm. 



I. Growth and Cell Division 22 



II. The Tropisms 24 



1 . Thermotaxis 24 



2. Galvanotaxis ". 25 



3. Chemotaxis. 29 



Conclusions 3 l 



INTRODUCTION. 



It has been known for several years that a marked similarity 

 in physical structure exists between protoplasm and that class of 

 chemical solutions known as colloidal solutions. This similarity 

 was pointed out by Hardy in 1899 as a result of his investiga- 

 tions upon the physical structure of certain organic colloids, as 

 egg albumen, gelatin, etc., which resemble protoplasm very 

 closely in their gross appearance, and of observations upon pro- 

 toplasm itself under various conditions. 



The conclusions of Hardy and others l in regard to the physical 

 structure of the organic tolloids are of such importance in the 

 further development of this paper, and are so largely unappre- 

 ciated by biologists, that they will be briefly recapitulated at this 

 place. 



i. A colloidal solution consists of a fluid matrix which holds 

 in suspension more solid or viscous granules (the colloidal par- 



1 Hardy, Jour, of Physio!., 1899, XXIV., p. 172; ibid., p. 288. Mann, 

 "Physiological Histology," Oxford, 1902. 



