The Food Factor in Hibernation. 



93 



and on two occasions i6° below. Notwithstanding this low 

 temperature the food was still eaten by the woodchucks. 



No food was supplied from Jan. 20 till Feb. 14 when the animals 

 were again examined in the burrows. On that day their tracks 

 in the snow were abundant. Six were found to be in a semitorpid 

 condition, but they did not show the deep narcosis of true hiberna- 

 tion; the others were very active and combative, one having a 

 rectal temperature of 99° F. Although no food had been placed 

 in the inclosure for three weeks, it is still possible that they had 

 some stored in their burrows, or that they ate the straw. 



The six which showed some degree of torpor were removed to 

 the laboratory, kept overnight outside the building in a large box 

 amongst straw, and the next day, under ether anesthesia, a 

 small lesion was made in the spinal cord of each. On the day 

 following they were completely awake and active, and remained 

 so until killed at various intervals after the operation. Food was 

 supplied to these as well as to those left behind in the burrows 

 from Feb. 14 onwards; they were inspected at short intervals from 

 that date till the end of March and never showed any tendency 

 to hibernate. The rectal temperature ranged from about 95 0 F. 

 to 101 0 F. 



These animals were not artificially protected from the weather 

 in any way; the only circumstance in which their condition dif- 

 fered from that of their fellows in the open fields was that food 

 was furnished them. The behavior of this colony would seem to 

 point to the fact, therefore, that the absence of food supply is 

 an important factor in determining the onset of hibernation. 



67 (676) 



A rapid method of producing a hemolytic serum. 



By FREDERICK P. GAT and J. 0. FITZGERALD. 



[From the Department of Pathology and Bacteriology, University of 



California.] 



Fornet and Miiller 1 were first to suggest the intensive method 

 of immunizing animals by giving large doses of serum for pro- 



1 Fornet and MUller, ZeUschrifl filr biotogische Technik und Methodik, Strassburg, 

 1908, vol. 1. p. aoi. 



