304 A. A. SCHAEFFER. 



toward that particle. As pointed out in a previous paper 

 (Schaeffer, 'i6b) in which the reactions of ameba toward proteins 

 are recorded, these isolated proteins, although insoluble enough 

 to satisfy the practical chemist that they may be classed as 

 'insoluble,' may nevertheless undergo an inappreciable amount 

 of solution sufficient to stimulate an ameba's sense organs. 

 There is however no direct means of knowing that such solution 

 takes place; it is nothing more than a possibility. It has 

 seemed practicable therefore to let the investigation of the be- 

 havior toward isolated insoluble proteins stand for the present, and 

 to test the reactions of ameba toward some of the purest and most 

 insoluble substances known to determine whether it is necessary 

 that a substance be soluble in order that an ameba may sense it 

 at a distance. In addition to these tests, a number of experi- 

 ments were also made with very soluble substances and with 

 solutions. 



The main conclusions of this paper are based on the reactions 

 toward carbon, glass, tyrosin and peptone. A sufficient number 

 of experiments with these substances are described and figured, 

 I trust, to illustrate, if not to prove, the conclusions. But in 

 addition to these, one or more typical experiments with each 

 one of various other substances have been figured to support 

 the conclusion that the behavior toward the substances specified 

 above is not directly dependent upon the chemical nature of the 

 substances, but upon their more generalized physical properties. 



REACTIONS TO CHEMICALLY INSOLUBLE INDIGESTIBLE 



SUBSTANCES. 



Carbon. This substance was prepared as follows. India ink 

 in stick form was boiled in xylol until the xylol remained clear. 

 The residue was washed in chloroform and then boiled in sul- 

 phuric acid, then filtered and washed with distilled water. The 

 residue was then boiled in potassium hydroxide solution. After 

 acidifying, the carbon was filtered and washed with distilled 

 w^ater acidified with hydrochloric acid. The carbon was then 

 dried and heated to redness for fifteen minutes in a closed 

 platinum crucible. This method of purification should have 

 removed all the soluble constituents present with the carbon in 

 the india ink. 



