PROFESSOR PAGET ON THE FREEZING OF THE ALBUMEN OF EGGS. 225 
points of albuminous solutions are lower than 32° in direct proportion to their den- 
sities ; they do not, in freezing-, rise to 32°, but freeze in all respects like saline solu- 
tions. And the same mode of freezing may be observed in organic tissues in which 
albuminous fluids are suspended or infiltrated. An eye, or its vitreous humour, a 
piece of muscle, gland, or brain, exposed to intense cold, loses temperature to 32° or 
3l^°, and remains at this, its freezing-point, till it is frozen hard throughout, and 
then descends to the temperature of the medium in which it is placed. 
The purpose or utility of this peculiar property of the albumen of eggs is manifest 
in the defence which it provides for eggs exposed to a temperature below 32°. If an 
egg be frozen, the damage sustained by its structure is such that the germ cannot be 
fully developed ; but mere cold, however intense, if freezing does not take place, does 
not prevent the complete development of the young bird. I placed three eggs in a 
freezing mixture, varying from zero to 5° Fahr. : one of them froze, and its shell 
was cracked from end to end ; another froze, and when it thawed, its yelk was burst 
and mixed with the albumen. In incubation, two spots of blood were developed in 
the former, and an enlargement of the cicatricula ensued in the latter of these two 
eggs, — sufficient indications that the intense cold and freezing had not killed them, 
though it had spoiled their structure. But in the third egg, which had been ex- 
posed for nearly an hour to a temperature below 5° Fahr., perfect development 
took place in incubation. Even this degree of cold therefore had neither killed nor 
frozen the egg, though, according to the average rate at which eggs part with heat, 
its whole substance must have been for half an hour at a temperature between 5° 
and 10° Fahr. 
This security of eggs from the injurious influence of cold has also been proved, on 
a large scale, by the ingenious inventor of the hydro-incubator, Mr. Cantelo. He 
has told me, that, to test the truth of the popular belief that eggs are always de- 
stroyed by exposure to a frosty air, he sometimes exposed baskets of eggs, through 
the whole of a Canadian winter’s night, to a temperature ranging, he believes, between 
5° and 10° Fahr. Some of them were cracked, and these he threw away ; they were 
doubtless frozen and spoiled ; but the rest were placed in his incubator, and the usual 
proportion were hatched. 
The need of such a provision against the influence of cold must exist in the case 
of many, or pei’haps of all, birds that breed in cold climates ; for accident must occa- 
sionally drive from their nests even those parent-birds that have not, like the common 
fowl, the custom of leaving their eggs for a certain time exposed to the open air. 
In conclusion, I may repeat that the experiments I have related show that it is not 
by the power of a vital principle that eggs resist the influence of cold. They show 
that certain things will destroy the power of resisting cold without affecting the ca- 
pability of being developed, and of therein manifesting the best evidence of life ; and 
that when eggs yield to the influence of intense cold, they are not damaged unless 
2 G 
MDCCCL. 
