DR DAVY ON THE FREEZING OF THE EGG OF THE COMMON FOWL.' 5 1 J? 



towards the surface and middle, which the congelation had not reached, it was 

 33 5°: and more remarkable still, when the albumen was frozen hard below, 

 above, where it was still liquid, it was 35°, a difference this strikingly illustrative 

 of the impediment offered to the mobility of the fluid by the tissue in question. 

 Another experiment with the thinner portion of the albumen of the same egg, 

 one which had been kept in lime-water upwards of twelve months, may be worthy 

 of notice in the way of further illustration. In this instance, after freezing, when 

 thawing was going on, and the albumen was perfectly liquid below, there the 

 thermometer was 32-5°, whilst towards the surface it was 31-75°, a difference, 

 owing, it may be inferred, to particles of ice ascending in the act of thawing. In 

 this trial congelation did not begin until the temperature of the fluid had fallen 

 to 20°. 



Besides the quality just mentioned, there is another, which probably has much 

 to do in retarding the freezing of the egg, — viz., the composition of its several 

 parts, and especially their saline elements, on the presumption of the well- 

 ascertained property which the soluble salts have in lowering the freezing point 

 of water, and how in aqueous solutions containing salts, such as common salt, 

 by augmenting the cold, a gradual concentration may be effected, a strong brine 

 may be obtained in contact with frozen water, or mingled with it. In some of 

 my experiments the appearance of the frozen albumen, in a soft state, at a tem- 

 perature below 32°, much resembled sea water suddenly frozen. 



I have mentioned in a preceding note the fluids contained in the egg in an 

 advanced stage of development. These, with the foetal chick, I subjected to the 

 action of a freezing mixture. The results obtained seemed in accordance with 

 what has been just stated. 



The very thin fluid next to the allantois or outer vascular membrane, froze 

 partially at 30-5° ; it was not completely frozen at 21°, a portion was still fluid at 

 the centre. The thermometer, as the freezing proceeded, rose to 31-5°, and it 

 continued at that temperature whilst thawing. 



The very thick viscid fluid fell to 23° before freezing began, though it was 

 stirred ; when the freezing took place, it rapidly rose to 31-25. The thin portion 

 of the yolk fell to 23° before it began to freeze, then it pretty rapidly rose to 

 31-75 ; when the thermometer was kept in this central, more fluid part, it was 

 31°. The results with the thicker portion did not differ materially. 



The foetus fell to 20°, and remained at that temperature some minutes without 

 freezing. 



.Whatever may be the cause or causes on which the resistance of the egg to 

 freezing (\epends, its possessing this property must be acknowledged to be a 

 happy circumstance in the animal economy, and an adequate security for the 

 preservation of its Ufe, or of that of the germ which the fertile egg contains, 

 and on which its after development into the chick depends, i.e., under the ordi- 



