322 PROPERTIES OF THE COLLOIDAL CONSTITUENTS 



suitable neutral salts. It is clear, therefore, that any constituent of 

 the cell which is responsible for these phenomena must be capable of 

 entering into combination with both acids and bases and with both 

 the acid and the basic radicals of salts. The Proteins are the only 

 abundant constituents of the cell which have been demonstrated to 

 possess these properties, and it has therefore been inferred by Loeb 

 and is now very generally assumed, that the toxicity of sodium salts, 

 for example, is attributable to the formation of sodium proteinates 

 which, if present in too great a proportion in the cell, confer upon the 

 protoplasm properties which are incompatible with the maintenance 

 of normal function. The toxicity of calcium salts is regarded as being 

 attributable in like manner to the undue predominance of calcium 

 proteinates in the cell. An admixture of several types of protein salts 

 is requisite to confer upon the protoplasm of the cell the exact complex 

 of qualities essential to the maximal furtherance of its vital activities. 



Much light has been thrown upon this question by two very striking 

 series of investigations, namely the Flotation Experiments of Loeb and 

 the Conductivity Experiments of Osterhout. The eggs of the marine 

 fish Fundulus which were employed in the earlier experiments cited 

 above have a specific gravity which is considerably in excess of that of 

 sea-water. They will float in a --- molecular solution of sodium 

 chloride, while they sink in a V~ molecular solution. The experiments 

 consisted in placing the eggs in solutions exceeding --f- molecular in 

 concentration, which is, of course, considerably hypertonic to the 

 contents of the eggs, and observing how long they will float in such 

 solutions. The withdrawal of water from the eggs is manifested not 

 only by shrinkage of volume, but by a coincident increase in specific 

 gravity which results finally in the eggs acquiring a higher specific 

 gravity than the medium so that they sink in it. Continued flotation 

 in hypertonic solutions is therefore evidence of impermeability of the 

 superficies of the cell for water. 



It is found that if the eggs are placed in a 3 molecular solution of 

 Sodium Chloride they will float, but as a rule not longer than three 

 hours. After that they sink to the bottom of the test-tube while the 

 loss of water which has led to their sinking is evidenced by collapse of 

 the egg-membrane, and shrinkage of the yolk-sac. When the eggs are 

 placed in a -/ molecular solution of Calcium Chloride they float at first, 

 but they sink in about half an hour. If, however, the eggs are placed 

 in a mixture of 50 c.c. of 3 molecular sodium chloride and 2 c.c. of --f- 

 molecular calcium chloride, they will float for three days or more at the 

 surface of the solution, the eggs shrink but little or not at all, and the 

 embryos continue to live. In a mixture of 50 c.c. of 2J m. NaCl + 1 

 c.c. of 2J m. KC1 + 0.75 c.c. of 2J m. CaCl 2 some of the eggs will con- 

 tinue to float for as long as ten days, while in a 2J m. solution of pure 

 sodium chloride they do not float for more than a few hours. 



These phenomena admit of only one explanation, namely, that in 

 normal sea-water the superficies of the Fundulus egg is practically 



