1 86 L. V. HEILBRUNN. 



gen by the passage of hydrogen, seemed to prevent the action 

 of hypertonic solutions upon sea-urchin eggs. He reasoned 

 from this that the hypertonic solutions produced an increase in 

 oxidations. In 1913 and 1914, I performed a number of ex- 

 periments with hypertonic solutions in the presence of KCN, 

 or in an atmosphere of hydrogen. In this paper I shall, however, 

 report only on the KCN experiments. The results obtained in 

 an atmosphere of hydrogen are perhaps more interesting, but 

 I do not feel as yet that every possible source of error has been 

 eliminated. 



At present it is generally accepted by most physiologists 

 that KCN suppresses cell oxidations. 1 Loeb states that 2 c.c. 

 1/20 per cent. KCN to 50 c.c. of sea-water suffice for the purpose. 2 

 In my experiments, a much higher concentration of the reagent 

 was employed. 



On August 19, 1913, I added 0.5 c.c. of I per cent. KCN to 

 every 58 c.c. of "NaCl hypertonic sea-water." (This addition 

 of only 0.5 c.c. of more concentrated reagent had the advantage 

 of not incurring as much dilution as the addition of 2 c.c. of 

 almost pure solvent.) Eggs were exposed to this cyanide-con- 

 taining "NaCl hypertonic sea- water," as well as to the normal 

 "NaCl" hypertonic sea-water. The results appear in the fol- 

 fowing table, in which the numerators of the fractions indicate 

 the number of eggs observed to segment, the denominators the 

 total number of eggs counted. Before return to sea-water, 

 the eggs which had been exposed to KCN were washed twice by 

 Lyon's test-tube method (Lyon '02), so that all trace of the poison 

 might be removed. 



" NaCl Hypertonic Sea- 

 Minutes Exposed. "NaCl Hypertonic Sea-water." water" plus KCN. 

 25 127/209 10/102 

 30 83/100 9/108 

 35 62/100 22/247 



Of the eggs exposed 25 or 30 minutes to the cyanide-containing 

 hypertonic solution, none went beyond the 2 (or 3)-celled stage, 

 but of the 22 eggs which segmented after an exposure of 35 

 minutes, two became many-celled blastulae and may have gone 



1 Personally I do not believe that the evidence in support of this view is con- 

 clusive. 



2 Loeb, '09, p. 55. 



