150 



Scientific Proceedings (59). 



92 (909) 



Laking of blood by freezing and thawing. 

 By C. C. Guthrie and M. E. Lee (by invitation). 

 [From the Physiological Laboratory, University of Pittsburgh.] 



The mechanism of laking by freezing and thawing 1 is not 

 understood. Since it is known that drying through evaporation 

 will cause laking, it is possible that drying through crystallization 

 of water 2 may account for laking by freezing. But again since 

 it is known that hypertonic solutions may cause laking, and since 

 there is evidence that the freezing point of serum is somewhat 

 higher than that of the intracellular liquids and therefore in freezing 

 a concentration of the serum solids occurs, it may be that such 

 laking is fundamentally the same as laking by hypertonic solutions. 



It was observed that blood could be repeatedly frozen and 

 thawed as in freezing point measurements with slight or no laking. 

 But when blood was exposed a single time to a temperature con- 

 siderably below the freezing point for some time, on thawing strong 

 laking occurred. To gain information on the question as to what 

 degree of cooling is necessary to cause laking and also as to the 

 relation of time of exposure to such temperature to the degree of 

 laking, the experiments, the results of which are herein reported, 

 were performed. The blood of various animals including ox, 

 dog, cat, and fowl has been used. Thus far no marked differences 

 in the behavior of the different bloods have been observed. 

 Summarized, the results show: 



1. That slight or no laking occurs when the temperature of 

 the blood is sufficiently lowered for the formation of crystals of 

 ice if the blood is maintained at this temperature for but a short 

 time. 



2. When maintained at a temperature between a point slightly 

 lower than that of the freezing point and minus one degree centi- 

 grade for ten minutes or more, laking occurs after the tube has 

 remained at room temperature for some time. 



3. The degree of laking, within limits, is proportionate to the 



^ollett, Sitzgsber. d. Wiener Acad., XLVI, S, 65, 1862. 

 2 Cf. Muller-Thurgan, Landw. Jahrb., XV, 534, 1886. 



