HIBERNATION IN MAMMALS— LYMAN and CHATFIELD 123 



Also, you show that circulation in the lower half of the hody is almost cut ofif. 

 Does shivering take place in that part of the body without circulation, or is there 

 any differrence between the upper and lower halves of the body? 



Dr. Lyman: In answer to the first question, we believe that during hibernation 

 the animal's circulation is vasodilated. Evidence of this is not derived from measure- 

 ment of peripheral blood flow or anything like that, but from the fact that in the 

 hamster, the only hibernator having unpigmented feet, the feet are bright pink 

 during the hibernating stage, but as soon as the animal starts to wake from hiber- 

 nation the feet become pale, showing, we think, vasoconstriction. Observing these 

 two things, we believe that the animal actually vasodilates as it goes into hibernation. 



As far as shivering is concerned, the front end of the animal shivers violently, 

 and it isn't until later when the blood supply is established that gross shivering 

 begins in the posterior part. In fact, an animal coming out of hibernation in the cold 

 room can crawl around with its front feet while it is still just dragging its rear end. 

 So it really becomes well organized in the anterior portion before the posterior 

 portion wakes up at all. 



Dr. McMurrey: I would lie interested in knowing how you get blood from an 

 animal analyzed for epinephrine or glucose while he is hibernating. 



Dr. Lyman: As far as the method I have used is concerned, the animal is really 

 in the very start of the waking process when the drawing of the blood is com- 

 pleted. Actually, from an animal such as the woodchuck I think you could get blood 

 from a chronically implanted cannula or something like that, but I have not at- 

 tempted to do it. What I do is pick up the animal and within about a minute I am 

 able to get blood from the heart by cardiac puncture. This animal isn't hibernating 

 in the true sense, because it has already started to wake up. On the other hand, the 

 slight changes which may take place in that short period should be smaller than the 

 errors in blood analysis. 



Dr. Henry Szvan: I just wondered, Dr. Lyman, if you would discuss the state of 

 the anesthesia in these animals during hibernation and during rewarming. I gather 

 from your discussion that most of these animals when recovering from hibernation 

 react to pain stimuli. 



Dr. Lyman: We have been able to get and evoke cortical potential at temperatures 

 as low as 7° C. by stimulating the peripheral sciatic nerve and picking up the 

 potential at the cortex. So apparently these animals do react at temperatures as low 

 as 7° C. The potential is a slow one, but it is there. 



Dr. Chandler McC. Brooks: I think this brings up a point of some interest. If 

 you remember the records of the action potentials in the hibernator at this crucial 

 period of 7 to 4° C, although the amplitude of the action potential of the nerve 

 was reduced, the area was greatly increased. Therefore, as far as the central nervous 

 system was concerned, an impulse going in at that time would be many times as 

 effective. It would act as a tetanus as far as the next synapse was concerned, com- 

 pared to that of the normal. So that is an interesting thing — why the nerve of the 

 hibernating animal retains this ability to be aroused when the other animals lost 

 it so much earlier. It is an inherent characteristic of the nerve. 



Dr. Lyman: In that regard, in the first record, I did point out that there were 



