17(i 



lia\'(' taken {jlace; «'i;i;s siibcoolcd and niaiiilaiiicd at -11° 

 tor 7 days were fluid on thawing'; .'>. Tlie malcrial must 

 stay a certain leug'th of time in the frozen condition; tlie 

 degree of stiffness increases with tli«d lengtli of time up to 

 about 20 hours and then it stays constant ; 4. Thawing 

 must not be too rapid; yoli-: immei-sed in licjuid air (24 

 hrs.) and then thawed at room temperature was pasty, 

 while it was fluid wiien thawed in mercury at + 30°. 



Moran explains these facts by assuming that the pro- 

 tein of the yollv, vitellin associated with lecitliin, wliich is 

 known to be soluble in lO''/ NaCl, gets dissolved in tlie 

 salt solution of the yolk wiien this solution is concentrated 

 by freezing. The "critical temperature of freezing," -6°, 

 would be the freezing point of that solution. On thawing, 

 the protein would irreversibly precipitate out. In an at- 

 tempt to verify this theory, he froze a dilute solution of 

 NaC^l containing some lecitho-vitellin and observed, on 

 thawing, a persistent cloud. 



During cooling and freezing, the yolk underwent some 

 unexpected changes in volume, which were measured with 

 a dilatometer. These changes can be summarized in the 

 4 following points : 1, The volume of the yolk exposed for 

 3 days at -11° and thawed decreased by 0.0084 of its origi- 

 nal value (measured at 0°) ; 2. The coefficient of expansion 

 of the thawed yolk was higher than that of the unfrozen 

 yolk; 3. The contraction of the normal unfrozen yolk, 

 which was linear with the temperature down to 0°, showed 

 a higher rate in the subcooled condition from 0° to -7° ; 

 4. The volume of the frozen yolk, measured at -7°, in- 

 creased by about 0.00015 of its original value when the 

 material stayed for 3 days at -11°, but it decreased below 

 the original value when the material stayed 9 days at -11°. 



Moran ascribes the decrease in volume resulting from a 

 long stay in the frozen state at -11° (under 4, above) to 

 the dissolving of the lecitho-vitellin of the yolk in the salt 

 solution; dissolving proteins has been observed often to 

 result in a decrease in volume. The long time involved 

 would !)(' a1ti-il)ntable to the breaking down of the struc- 



