HIBERNATION IN MAMMALS— LYxMAN and CHATFIELD 



111 



lOOmsec 



100 msec. 



Fig. 22. — C.R.O. records of an evoked potential from strychninized cortex in an anaesthetized 

 hamster on stimulation of the ipsilateral sciatic nerve showing the resistance of subcortical 

 relays to cooling. A, B, and C show a series of shocks ; D and E, responses to single shocks. 

 Note that the cortical potential occurs only in response to the first shock of a series. Other de- 

 flections in records A, B, and C are artefacts from EKG. The latency of the response increases 

 on cooling from 50 msec, in record A to 115 msec, in record D. Calibration after record D is 

 for records A-D. Records E, after rewarming the animal. Latency 55 msec. Calibration after 

 record E is for record E alone. Cortical temperatures: A = 11.7, B = 10.8, C = 9.4, D = 9.1, 

 E = 13.6° C. 



to cold because fast frequency, low voltage activity was the last to appear during 

 arousal. The intralaniinar thalamo-cortical circuits were felt to be second in order 

 of resistance since spontaneous burst activity appeared before the fast frequency 

 discharges. Spino-bulbo-thalamo-cortical relay systems and the cortex itself were 

 judged to be more resistant than either of the preceding since the cortex was elec- 

 tricall}^ excitable and an evoked potential could be obtained even at low temperatures. 

 In an extension of this investigation, Chatfield and Lyman"^ explored the cerebral 

 hemispheres and brain stem of hamsters during the process of arousal and were able 

 to record electrical activity at much lower temperatures than those at which spon- 

 taneous cortical activity occurred. The electrical activity recorded early in the 

 process of arousal was obtained almost exclusively from components of the limbic 

 system (fig. 23). These results strongly imply that it is the discharge of the limbic 

 system, prol^ably with the hypothalamus as a relay station, that initiates and co- 



at the right. A large amount of glycogen is uniformly distributed throughout the lobule. Chemi- 

 cal determination of glycogen content : 40.9 mg./gm. X 1-5. 



2 — Liver of the same animal fixed 34 minutes later when cheek-pouch temperature had risen 

 to 11° C. Glycogen loss is evident throughout the lobule but is more pronounced in the central 

 zone. Chemical determination of glycogen content : 33.2 mg./gm. X 125. 



3 — Liver of the same animal fixed when arousal was complete, 130 minutes after the beginning 

 of waking. Glycogen concentration has diminished further throughout the lobule. It is abundant 

 only in those cells contiguous to the portal canal, almost absent in the middle zone of the lobule, 

 and irregularly distributed in a mosaic pattern in the central zone. Chemical determination of 

 glycogen content : 8.4 mg /gm. X 125. 



4 — Cardiac muscle from a control hamster maintained in a warm environment. A very small 

 amount of glycogen can be detected as fine dark granules deposited along one side of each muscle 

 fiber. Chemical determination of glycogen content : 2.13 mg./gm. X 300. 



5 — Cardiac muscle from a normal hibernating hamster. Glycogen is much more abundant 

 than in control above. Chemical determination of glycogen content : 4.04 mg./gm. X 300. 



6 — Cardiac muscle from a hibernating hamster which had been deprived of food. A heavy ac- 

 cumulation of glycogen is present throughout all muscle fibers. Chemical determination of 

 glycogen content : 8.56 mg./gm. X 300. 



