The Freezing Point of Yolk and White of Egg: Note on the ForegoingAuthor(s): William HardySource: Proceedings of the Royal Society of London. Series B, Containing Papers of aBiological Character, Vol. 112, No. 779 (Apr. 1, 1933), pp. 477-479Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/81598 .

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The Freezing Point of Yolk and White of Egg. The Freezing Point of Yolk and White of Egg.

The freezing point of both thin and thick white therefore lies between -0 41? and --042? C.

It is important to note that in all the above experiments the time in days at which a certain change is noted does not mean that the change, e.g., freezing, had not taken place earlier: it means simply that for one reason or another it had not been thought advisable or had not been possible to examine the pails earlier.

Note on the foregoing by Sir WILLIAM HARDY, F.R.S.--Recent work on the

osmotic pressure of the hen's egg has introduced a sense of uncertainty as to the value of the many comparisons which have been made between osmotic

pressures of the blood, body fluids, and surrounding media. The uncertainty

pertains not to theory but to a simple matter of fact and, as this involves that most fundamental datum for biological theory-viz., the state of the water in the living cell-there is urgent need to have it cleared up. The fact in

dispute is the freezing point of the yolk and white of the bird's egg. Atkins in 1909 by measurements, obviously made with the greatest care, found " no

difference between the freezing point of white and yolk of the same egg and a, mixture of white and yolk gave the same depression."

Atkins (1909) used the ordinary Beckmann technique and so, too, did Straub (1929) twenty years later, but with a surprisingly different result for

he found a constant difference between white and yolk of the hen's egg amount-

ing on the average to --0 15? C. A. V. Hill (1930) confirmed Straub's (1929) finding by a different method. HIe compared the fall in temperature caused

by evaporation with that of water and from the difference calculated the osmotic pressure. Howard (1932) using the Beckmann method again found no difference in the freezing point of white and yolk. In these measurements the yolk was puddled by stirring so that at sometime or another the structure was broken down. Yolk is not only a chemical complex but it is alive, gross mechanical disturbance might, therefore, have the effect it usually has on

living cells and cause chemical breakdown with consequent fall of the freezing point. Hale's experiments were designed to explore this possibility by observing directly the freezing point of intact yolk and white.

The difficulties in the way are obvious and not easily overcome. Consider a yolk covered with white with a column of ice, started in the white by seeding, approaching the yolk. When the ice meets the vitelline membrane one of two things may happen: ice may penetrate the pores of the membrane to seed the yolk, or water may move from the yolk to the membrane to con- dense on the ice face. The second possibility follows from Moran's (1926)

The freezing point of both thin and thick white therefore lies between -0 41? and --042? C.

It is important to note that in all the above experiments the time in days at which a certain change is noted does not mean that the change, e.g., freezing, had not taken place earlier: it means simply that for one reason or another it had not been thought advisable or had not been possible to examine the pails earlier.

Note on the foregoing by Sir WILLIAM HARDY, F.R.S.--Recent work on the

osmotic pressure of the hen's egg has introduced a sense of uncertainty as to the value of the many comparisons which have been made between osmotic

pressures of the blood, body fluids, and surrounding media. The uncertainty

pertains not to theory but to a simple matter of fact and, as this involves that most fundamental datum for biological theory-viz., the state of the water in the living cell-there is urgent need to have it cleared up. The fact in

dispute is the freezing point of the yolk and white of the bird's egg. Atkins in 1909 by measurements, obviously made with the greatest care, found " no

difference between the freezing point of white and yolk of the same egg and a, mixture of white and yolk gave the same depression."

Atkins (1909) used the ordinary Beckmann technique and so, too, did Straub (1929) twenty years later, but with a surprisingly different result for

he found a constant difference between white and yolk of the hen's egg amount-

ing on the average to --0 15? C. A. V. Hill (1930) confirmed Straub's (1929) finding by a different method. HIe compared the fall in temperature caused

by evaporation with that of water and from the difference calculated the osmotic pressure. Howard (1932) using the Beckmann method again found no difference in the freezing point of white and yolk. In these measurements the yolk was puddled by stirring so that at sometime or another the structure was broken down. Yolk is not only a chemical complex but it is alive, gross mechanical disturbance might, therefore, have the effect it usually has on

living cells and cause chemical breakdown with consequent fall of the freezing point. Hale's experiments were designed to explore this possibility by observing directly the freezing point of intact yolk and white.

The difficulties in the way are obvious and not easily overcome. Consider a yolk covered with white with a column of ice, started in the white by seeding, approaching the yolk. When the ice meets the vitelline membrane one of two things may happen: ice may penetrate the pores of the membrane to seed the yolk, or water may move from the yolk to the membrane to con- dense on the ice face. The second possibility follows from Moran's (1926)

477 477

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The Freezing Point of Yolk and White of Egg.

observation when he found that ice formed wholly on the surface of disks of

gelatine gel, provided the rate of cooling was slow and that a true reversible

equilibrium obtained between gel and ice over a large range of temperature. This must happen if the surface separating ice and gel is plane for, the specific volume of ice being greater than that of water, the formation of ice within the

gel would be resisted not only by the positive energy of the new interface, but also by the general cohesion of the gel.

A curious feature about phase lag in the liquid or gel state is the existence of a time limit to overcooling. Why should over-cooling, when once estab-

lished, not be permanent ? The answer, I think, introduces another cause of

phase lag, namely, the time taken to orient complex molecules at the new interface. This seems to be the simplest explanation. It takes an hour for a monomolecular film of a fatty acid adsorbed on to a plane solid face to reach

equilibrium at ordinary temperature. It is not surprising, therefore, that the orientation needed for the formation of a new interface can take days when the temperature is below the freezing point.

As a minor point Hale's experiments show that the intact vitelline membrane

permitted ice to pass to the yolk at --0 650 C. Taking the freezing point of

yolk at -0 -57? C. it was able to resist no more than --0 08 C. of overcooling. But " intact " yolk must not be taken to mean a yolk with a wholly uninjured membrane for in the act of breaking the yolk into a pail the membrane was obviously violently stretched.

The existence of a difference in the freezing point of yolk and white is fully confirmed and that implies a difference in osmotic pressure, but there is no difference in hydrostatic pressure greater than a delicate, elastic, though possibly tough, membrane such as the vitelline membrane can bear.

The clue to this paradox seems, however, to be simple. It lies in two things: the hindrance to the movement of water in yolk and thick white and the slow

leakage of water through the vitelline membrane which, as eggs age, lessens the difference between the average osmotic pressure of yolk and that of the white. It is as though there were a number of chokes between a household water tap and the reservoir which together reduced the flow to a trickle. So

long as that trickle is unimpeded the pressure difference at the tap is negligible. Try to stop it with the thumb, however, and the whole pressure from the reservoir has to be held back.

I suggest that there is in the egg no sharp change of pressure at either of the surfaces of the vitelline membrane, but there is a gradient from the centre of the yolk outwards of varying, but always slight slope which ends

478

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Blood Circulation of Animals Possessing Chlorocruorin. 479 Blood Circulation of Animals Possessing Chlorocruorin. 479

at a surface whose position depends upon the rate of evaporation from the

shell. Evidence for a hindrance to the movement of water can be found scattered

through the paper by Smith and Shepherd (1931), in Moran's (1925) observation that yolk can be readily overcooled-even broken yolk can be held

at -7 4? C. and in the various phase lags revealed by Hale's experiments.

REFERENCES.

Atkins (1909). 'Proc. Roy. Dublin Soc.,' vol. 12, p. 123.

Hardy (1926). ' Proc. Roy. Soc.,' A, vol. 112, p. 47. Hill, A. V. (1930) ' Proc. Faraday Soc.,' Symposium. - (1930). 'Proc. Roy. Soc.,' B, vol. 106, p. 477.

Howard (1932). ' J. Gen. Physiology,' vol. 16, p. 107. Moran (1925). 'Proc. Roy. Soc.,' B, vol. 98, p. 436.

(1926). ' Proc. Roy. Soc.,' A, vol. 112, p. 30. Smith and Shepherd (1931). 'J. Exp. Biol.,' vol. 8, p. 293. Straub (1929).

' Rec. Trav. Chim. Pays Bas,' vol. 48, p. 49.

612. 13:595. I7

The Blood Circulation of Animals Possessing Chlorocruorin.

By H. MUNRo Fox, Professor of Zoology in the University of

Birmingham.

(Communicated by J. Stanley Gardiner, F.R.S.-Received January 12, 1933).

Some of the chemical and physico-chemical characteristics of the respiratory blood pigment chlorocruorin have been dealt with in previous papers (H. M.

Fox, 1926, 1932). An experimental investigation is described below of the blood circulation in sabellids and serpulids. These polycheete worms have

chlorocruorin in solution in their blood plasma. The work was done in part in the Marine Biological Laboratories of Banyuls, Plymouth, and Tamaris, and my sincere thanks are due to the Directors and staffs of these institutions for their welcome and help.

1. The Normal Blood Circzlation.

In sabellids and serpulids both the anatomy of the blood system and the mode of blood circulation are peculiar and different from those in other poly- chaete worms. The best description of the anatomy of the blood system is that of Meyer (1888).

at a surface whose position depends upon the rate of evaporation from the

shell. Evidence for a hindrance to the movement of water can be found scattered

through the paper by Smith and Shepherd (1931), in Moran's (1925) observation that yolk can be readily overcooled-even broken yolk can be held

at -7 4? C. and in the various phase lags revealed by Hale's experiments.

REFERENCES.

Atkins (1909). 'Proc. Roy. Dublin Soc.,' vol. 12, p. 123.

Hardy (1926). ' Proc. Roy. Soc.,' A, vol. 112, p. 47. Hill, A. V. (1930) ' Proc. Faraday Soc.,' Symposium. - (1930). 'Proc. Roy. Soc.,' B, vol. 106, p. 477.

Howard (1932). ' J. Gen. Physiology,' vol. 16, p. 107. Moran (1925). 'Proc. Roy. Soc.,' B, vol. 98, p. 436.

(1926). ' Proc. Roy. Soc.,' A, vol. 112, p. 30. Smith and Shepherd (1931). 'J. Exp. Biol.,' vol. 8, p. 293. Straub (1929).

' Rec. Trav. Chim. Pays Bas,' vol. 48, p. 49.

612. 13:595. I7

The Blood Circulation of Animals Possessing Chlorocruorin.

By H. MUNRo Fox, Professor of Zoology in the University of

Birmingham.

(Communicated by J. Stanley Gardiner, F.R.S.-Received January 12, 1933).

Some of the chemical and physico-chemical characteristics of the respiratory blood pigment chlorocruorin have been dealt with in previous papers (H. M.

Fox, 1926, 1932). An experimental investigation is described below of the blood circulation in sabellids and serpulids. These polycheete worms have

chlorocruorin in solution in their blood plasma. The work was done in part in the Marine Biological Laboratories of Banyuls, Plymouth, and Tamaris, and my sincere thanks are due to the Directors and staffs of these institutions for their welcome and help.

1. The Normal Blood Circzlation.

In sabellids and serpulids both the anatomy of the blood system and the mode of blood circulation are peculiar and different from those in other poly- chaete worms. The best description of the anatomy of the blood system is that of Meyer (1888).

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