SCHMIDT 



The resistance of hibernating animals to infection has been in- 

 vestigated by Kalabukhov (1958) and others. The available evidence 

 indicates that resistance to infection is increased duringthe period 

 of preparation for hibernation as well as during hibernation. There 

 is general agreement that the enhanced resistance is simply a re- 

 flection of the physiological state of the animal. Since the infectious 

 agents tested are not capable of reproduction at temperatures found 

 in the hibernating host, one would not expect to find evidence of an 

 active infection under such conditions. At the same time, one might 

 expect very little phagocytic activity at such reduced temperatures, 

 and it is known that a leucopenia occurs during hibernation (Svihla, 

 19 53). These observations would suggest that increased resistance 

 in the hibernating state is probably not related to the cellular mech- 

 anisms of resistance. 



Adequate data are not available concerning the humoral resistance 

 of hibernators, Jaroslow and Smith (1961) have studied the disappear- 

 ance of antigen from the circulatory system of hibernating ground 

 squirrels. Their data indicate that there is little or no disappearance 

 of homologus or heterologus proteins from the circulation during 

 periods of hibernation. Studies concerning the actual production of 

 antibody during hibernation are lacking. 



In our bacterial studies we have shown that the psychrophiles 

 grow well at temperatures downtoO°C, and that they increase con- 

 siderably in number in the intestinal tract during hibernation. Most 

 of the psychrophilic organisms we have encountered have been gram 

 negative rods and producers of endotoxin. It is conceivable that with 

 the animal's normal mechanisms of resistance either inoperative or 

 functioning with reduced efficiency,these organisms might find their 

 way out of the intestinal tract and into other parts of the body such 

 as the blood stream. It is tempting for me to speciilate that one of 

 Nature's reasons for programming those unexplained spontaneous 

 arousals, which are accomplished at great expense of energy to the 

 animal, might be to clear the circulation of these and other invading 

 toxic elements. One of the things we plan to do in the future is 

 to check the blood of the hibernating squirrels for psychrophiles 

 and other endogenous microorganisms. 



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