PROBLEMS Op- I IKMATOI.OGY— CROSBY 185 



surfacc-coolcd to Ixuly Icinperaturcs of approximak-ly 20° C. The platelets fell to 

 quite low levels, 6,000 to 60,000, as the animal was cooled, and then recovered as 

 it was warmed. The changes in the coagulation mechanism could be accounted for 

 on the basis of thrombocytopenia: the alterations of bleeding time, clotting time, 

 prothrombin consumption, and so forth. The leukocytes also disappeared and then 

 reapj)eare(l. 



This left us with several problems. W hat happened to the i)latelets and leuko- 

 cytes? When the platelets and leukocyte counts returned to normal, were these the 

 same cells which had been in the l)lo(xl before hypothermia, or was this a new 

 population ? 



Figure 2 shows another change which occurred, an increase in hematocrit in most 

 of the animals which recovered rather more slowly than the changes in platelets and 

 leukocytes. 



A preliminary experiment (fig. 3) by Dr. W. A. O'Brien seemed to indicate that 

 the change in hematocrit was due to a temporary loss of plasma from the circulat- 

 ing blood. 



With this as an introduction, I would like to present Dr. Adelson, who will dis- 

 cuss the changes which take place in the platelets and leukocytes during deep 

 hypothermia. 



