510 DR DAVY ON THE FREEZING OF THE EGG OF THE COMMON FOWL. 



30° and 31°, the freezing making progress. When the greater portion was frozen, 

 the thermometer, where the freezing had not reached, showed the temperature 

 last mentioned. 



The experiment was repeated on another portion of the same yolk. In it the 

 thermometer fell to 22° without the occurrence of freezing ; it was taken out, 

 wiped, and returned ; it fell to 28°, and continued at that degree several minutes, 

 the yolk remaining liquid. It was again taken out and wiped, and returned, it 

 fell to 30°, and almost immediately freezing took place at the circumference, 

 whilst in the middle the yolk was still fluid, though the thermometer there stood 

 at 28°, after that it rose to 31° and to 31-25°. 



With the yolk from an egg kept in lime-water, the thermometer fell to 20° 

 before freezing began at the circumference, it then rose as the freezing proceeded 

 to 31-25°. 



Another portion of the same yolk fell to 28° before freezing began ; the ther- 

 mometer then rose rapidly to 31-25°. 



The albumen, whether thick or thin, showed the same irregularities in freez- 

 ing. On what they depend I hardly venture to offer an opinion ; perhaps the 

 strength of the freezing mixture is most concerned, yet the trials made to endea- 

 vour to determine this were nowise satisfactory. 



In all the experiments which I have made on the freezing of the contents of 

 the egg by a freezing mixture and by ether, the congelation, as might be 

 expected, always began at the circumference, gradually extending towards the 

 centre ; it was remarkable, unless the freezing mixture was powerful, how slowly 

 it proceeded, the centre being often soft, whilst the surrounding part was hard ; 

 and from the circumstance that concentric rings were often seen in a portion of 

 yolk entirely frozen, as noticed in the instance of the egg, it seems probable that 

 the congelation was in a manner paroxysmal. The moving of the thermometer, 

 even to active stirring, in the fluid, seemed to have little or no effect in hastening 

 the freezing, even at 20° or below 20°. 



Mr Paget lays stress on the low degree of temperature which the egg bore 

 in his experiments before its freezing took place, a result with which mine, con- 

 ducted in the open air on the entire egg, hardly accord. He, as already remarked, 

 is disposed to attribute this resistance of the egg to the peculiar viscid and tena- 

 cious state of the albumen. That this viscous state, and more especially the cel- 

 lular filamentous tissue in which the albumen is retained, and to which the 

 viscidity is very much owing, may be concerned in part, can hardly be doubted. 

 It appears to operate by checking the motion of the fluid from change of specific 

 gravity, depending on change of temperature, as in the instance of water. The 

 following experiments may be mentioned in proof: — 



The thick albumen of an egg was plunged into a freezing mixture ; congela- 

 tion took place at the bottom and sides, there the thermometer was 31-5°, whilst 



