. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 62 OVUM. process, and in eggs that have been long kept, the space has extended over the whole width of the egg, and the quantity of gas contained in this space is sufficient to cause the eggs to float in water. The extent of the air-space may be ascertained in some degree by the greater or less feeling of coldness of the shell of the egg near the obtuse end, when it is applied to the skin of a delicate part, such as the eyelid, in consequence of the heat being less rapidly carried off by that part of the shell within whi
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 62 OVUM. process, and in eggs that have been long kept, the space has extended over the whole width of the egg, and the quantity of gas contained in this space is sufficient to cause the eggs to float in water. The extent of the air-space may be ascertained in some degree by the greater or less feeling of coldness of the shell of the egg near the obtuse end, when it is applied to the skin of a delicate part, such as the eyelid, in consequence of the heat being less rapidly carried off by that part of the shell within which the air-space has been formed, than at others with which the albumen is in contact. Dr. Paris found this air, amounting to about half a cubic inch, to be nearly pure atmo- spheric air, with a small quantity of carbonic acid towards the end of the period of incuba- tion. MM. Baudrimont and St. Ange find it to contain in general more oxygen than atmospheric air, and no carbonic acid; whence they conclude that the shell has a peculiar power of passing outwards the carbonic acid formed during incubation and taking in oxygen.* The formation of the air-space is manifestly a compensation for the loss of sub- stance in whatever way occasioned, that may take place from the egg. We shall have oc- casion afterwards to consider in how far it may be important in connection with the phenomena of incubation. The specific gravity of the whole egg, when newly laid, and before evaporation has taken place, is generally as high as 1090, being raised considerably above the common spe- cific gravity of the fluids and soft parts of animals by the superior density of the shell; but as the air space increases, the whole spe- cific gravity will be lowered. The specific gravity of the albumen and yolk differ in a considerable degree; that of the yolk, though containing the largest amount of solid matter, being lowest in con- sequence of the large quantity of oily matter belonging to it; and thus when
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