CHROMATOLYTIC CHANGES DURI^XI HIBERNATION 393 



are no changes. In reptiles, however, Zalla did find a marked 

 decrease during torpoi-. 



Some other morphological changes in the nerve cells during 

 hibernation may be briefly mentioned. Querton ('98) bj' means 

 of the Golgi method on cerebral neurones found that the pro- 

 toplasmic prolongations retract and assume a moniliform ap- 

 pearance during the dormant period. This, however, could not 

 be substantiated b}' Baroncini and Beretta ('00). Some work 

 has been done on the neurofibrillae. Tello ('03) reported that 

 in the motor cells of the spinal cord of lizards the neurofil:)rillae 

 are much thicker than usually found. Tello and Cajal ('04) 

 found that this was true only during the cold season when the 

 animal is dormant, and that when the animal is warmed up and 

 made active the fibrillae become more numerous and much 

 finer. Cajal thus believes that the hy]KMti-()])hy of the neuro- 

 fibrillae is due to the cold and resulting diminished s])inal reflexes, 

 bcc.Musc exposure (»r llic nniiiial t<. a low temperature brought 

 about this gi'-ntisni of the ii('Ui<.lii)rillae while warming it up 

 caused a i-ctui-n 1(» llic iK.inial. and l)ec;'use this change is not 

 seen in the telence])hal()n and mesencei)halon whose cells retain 

 their activity to a nuich greater extent during the lethargA'. 

 jNIarinesco CO')) has re]ieatetl these ex])erhnents on young cats 

 and dogs and Dustin ('()()) has done the same on young rabbits 

 with essentially shnilar results. A temjierature below 10°C., 

 however, was found to be less effecti\e than 10°C. in bringing 

 about these changes in the neurofibrillae, according to iMarinesco. 

 This may be related to the fact that a temj^erature too low excites 

 hibernating mannnals and Anally wakes them up since the body 

 temperature rises as a result of increased actiA'ity. The latter 

 author found no such modification of the fibrillae in hibernating 

 hedgehogs, which fact he interprets as indicating that the activity 

 of the nervous system of hibernating mammals is not reduced to 

 the extent that it is in the lizard and other cold blooded animals. 

 Zalla ('10), on the other hand, found that the neurofibrillae were 

 fewer and farther apart in the dormouse during hibernation. 



