Ntjva Acta AcademiiB Naturae Curiosorum. 251 



of his zealous perseverance in the career of science. Dr. Otto passes 

 over the opinions of the older writers as to the cause of the hybernation 

 of some among the Mammalia, and mentions those only of Mangil and 

 Saissy. The explanation of this phaenomenon given by the former was 

 founded on the statement that in these animals the anterior or carotid 

 cerebral artery was entirely wanting, the whole supply of blood received 

 by the brain being furnished by the posterior cerebral alone : hence he 

 concluded that the irritability of the brain was diminished, and that 

 consequently a longer period of rest was required by them than by other 

 quadrupeds to renovate its exhausted vigour. The foundation of this 

 theory gives way at once before the fact established by the repeated dis- 

 sections of Dr. Otto, that in all hybernating quadrupeds, without excep- 

 tion, both these arteries exist, the carotid cerebral being however of 

 small size and liable to escape the notice of an inattentive observer on 

 account of its unusual course through the cavity of the tympanum. The 

 number and capacity of the cerebral vessels in general, he asserts to be 

 fully equal to those of other animals of equal size. The theory of 

 M. de Saissy on the other hand rests on his recorded observations that 

 the heart and internal vessels in hybernating animals were more capacious, 

 while the external were less so, and the cutaneous nerves larger in pro- 

 portion, than in other Mammalia: hence he concluded that the former 

 were more obnoxious to the influence of cold. But the fact here as- 

 sumed is positively contradicted by the observation of Dr. Otto, who 

 declares that no appreciable difference exists in either respect between 

 the animals in question and the rest of the class. He details with great 

 minuteness a long series of dissections, principally of the cerebral 

 vessels and internal ear, of more than fifty quadrupeds, mostly of the 

 order Rodeivtia, to which the hybernating species almost exclusively 

 belong. The most striking and uniform result of these investigations is 

 the fact, that in all such animals the carotid cerebral enters the cranium 

 through the foramen jugulare, or in its immediate neighbourhood, and 

 passes across the cavity of the tympanum, and through the stapes, in its 

 singular and tortuous course to the brain itself. But although this pecu- 

 liar structure obtains thus universally in hybernating animals, our au- 

 thour is by no means of opinion that it can be considered as the cause of 

 their propensity to continued sleep ; on the contrary, he regards this ex- 



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