358 LEWIS V. HEILBRUNN. 



tion lowered the surface tension of water by almost one fourth 

 of its value. As was expected, therefore, membrane elevation 

 was produced when a few crystals of chloretone were added to 

 sea-water containing eggs. 



Ur ethane. According to an approximate determination, a 0.5 

 M solution of urethane has a surface tension of about 61.3 dynes 

 per centimeter, a value considerably below that of pure water. 

 Hence all solutions of urethane produce membrane elevation 

 (and cytolysis) whether they be isotoni'c, hypotonic, or hyper- 

 tonic. Solutions of urethane in sea-water likewise give results, 

 although this substance is not as effective as chloretone. 



Chloral Hydrate acts in similar fashion to chloretone and 

 urethane. 



Esters. All esters possess the property of lowering surface 

 tension. 1 The following esters were used and proved effective in 

 producing membrane elevation. Methyl acetate, ethyl acetate, 

 ethyl butyrate, methyl salicylate. 



The substances which lower surface tension are very numerous 

 Not all, however, produce membrane elevation. In general, there 

 are three classes of exceptions. 



1. Colloids. Many proteins lower surface tension but do not 

 cause membrane elevation. 



2. Protein Coagulants. If the solution is strongly coagulative, 

 no sign of membrane elevation will appear. However, if the 

 coagulative action is not very strong, or if the surface tension is 

 quite low, membranes are often pushed out. Under these condi- 

 tions, a number of little elevations, the so-called "bubbles" or 

 "blisters" are often seen to surround the egg. Loeb and his 

 pupils consider these "blisters" as a preliminary stage in mem- 

 brane elevation, but they can be observed only when a protein 

 coagulant is present. By adding protein coagulants and at the 

 same time lowering the surface tension, "blister" formation can 

 always be induced. For example, if the eggs are subjected to 

 a solution of acetamide, which contains free acetic acid, they 

 immediately become surrounded with blisters. Similar results 

 are gained with aqueous solutions of picric acid. If the surface 

 tension is low enough, membranes sometimes are formed. 



1 Cf. J. Traube, Ber. d. deutsch. chem. Gesellsch., XVII., 2294 (1884). 



