DR DAVY ON THE FREEZING OF THE EGG OF THE COMMON FOWL. 509 



As the results of the foregoing experiments seem to show that there is no well- 

 marked difference as to freezhig between the newly laid egg and the egg which 

 has been kept many months, nor any well-marked difference as to their rise or 

 fall of temperature, they appear to support Mr Paget' s conclusion, that the egg 

 is not protected under these trials by a vital principle, as supposed by Hunter. 



There are other experiments which I have made, which seem to have the same 

 tendency. These have been on the freezing of the different parts of the egg by 

 ether, and a freezing mixture in a thin glass tube. The advantage of this 

 method is, that what occurs is seen, and one is thus better acquainted with the 

 particulars. 



Owing to the peculiar qualities of the contents of the egg, the subject is 

 obscure and difficult, and it is not easy to arrive at consistent and altogether 

 satisfactory results. 



My first object was to endeavour to ascertain the temperature at which the 

 several contained parts freeze. From many trials, I am led to infer, that the 

 freezing point of the thinner albumen is Sl-TS", of the thicker 31-50°, and of the 

 yolk 31*25° ; and that comparing those of the newly laid egg with those of the 

 egg long kept in lime-water, there is no well-marked difference. Whether such 

 results might be expected, I hardly venture to form an opinion, not knowing to 

 what extent the two differ in composition. That there is a difference, has 

 already been noticed in the appearance of the yolk, and in the quantity of air 

 contained; and another slight difference I have observed, — viz., that whilst the 

 yolk of the newly laid egg has an acid reaction, that of the long-kept egg is 

 neutral. 



Owing to conflicting results, and many repetitions in consequence, it would be 

 tedious to give the particulars of the many experiments which I have made. One 

 or two examples I shall offer, and this chiefly with a view to show the variability 

 of the freezing point. 



The trials were made in a tube -7 inch in diameter of thin glass. The ther- 

 mometer, a very delicate one, was introduced with the fluid, and was often 

 moved. As the results with a freezing mixture were least unsatisfactory, I shall 

 confine myself to them. 



In the yolk of a newly laid egg the thermom eter fell to 20° without freezing 

 occurring. It was taken out freed from adhering yolk, and again immersed ; it 

 fell to 28"^, presently freezing began at the circumference, the thermometer in the 

 centre continuing at 28°, where the yolk was still fluid ; pretty rapidly it rose to 



yellow. In both eggs, between the yolk and the white, there was a greyish discoloration. The 

 quantity of air that was disengaged from the egg long kept was remarkable. I supposed that it 

 might be carbonic acid or azote ; but from one examination I made of it, it appeared to be merely 

 common air. Owing to this circumstance, eggs thus kept, or kept long otherwise, crack, and some- 

 times with a little explosion, when put into boiling-water ; the newly laid, which contain very little 

 or no air, not being subject to the same effect, — the exemption may be held to be characteristic, 



VOL. XXIII. PART III. 6 Y 



