50 



THE EDINBURGH JOURNAL OF NATURAL HISTORY, 



0^ THE HYBERNATION OF AMMALS. — NO. III. 

 We shall now examine more in detail the distinguishing Physiological Conditions 

 of this interesting class of animals, and first shall make some observations on their 

 Respiration. 



It has been ascertained by experiment that all the warm-blooded animals, when 

 asleep, consume less oxygen than when awake. In tlie hybernating animals, during 

 their lethargic state, this is carried to a much greater extent. Mangili carefully observed 

 the fat Dormouse (Mits Gils) in this state, and found that its respirations were irregu- 

 lar, with long intervals between them: at one time the animal breathed from 13 to 15 

 times in succession, then followed an intermission of from 24 to 28 minutes, without 

 apy respiration. In another Dormouse (Mus avellanarius) he found its respiration 

 only 3 in the minute, though the temperature was as high as Qb^. Prunelle placed 

 a Hedgehog, in a state of lethargy, under water for 4 minutes, without injury to 

 the animal. He also found the respirations so imperfect, in a state of lethargy, when 

 the temperature was about 44" or 45" that they could not be reckoned. They became 

 sensible when the temperature was raised to 59", and in a low temperature they were 

 3 or 4 per minute, with intervals. Dr Marshall Hall has made the most accurate 

 experiments upon this point, and they fully bear out the statements made by Mangili 

 and Prunelle, that the function of respiration is nearly suspended. He placed a 

 lethargic Bat under an instrument which he has invented for experiments of this 

 kind, and which he has termed a pneumatometer, for 10 hours, and found no percep- 

 tible absorption of oxygen. He then roused the animal, and the absorption became 

 immediately apparent. Another lethargic Bat was placed 24 hours under the instru- 

 ment, and a cubic inch of the oxygen only had disappeared. A Bat placed sixty 

 hours under the instrument, at a temperature varying from 38" to 41^, occasioned an 

 absorption to the extent of 3.8 inches. In a state of activity equal quantities of gas 

 disappeared in less than half that number of minutes. 



He retained a lethargic Bat for 16 minutes, and a lethargic Hedgehog for 22^ 

 minutes, under water, without any injurious eifects. The same animals, in a state of 

 activity, expire when placed under water for three minutes. Spallanzani enclosed 

 a Marmot and a Bat for four hours in carbonic acid gas without injury. 



Great care should be taken, in an experiment of this kind, to observe that the ani- 

 mal is sufficiently lethargic, and that it does not become roused, for immediately the 

 respiration becomes more frequent, more oxygen is consumed within a given time, 

 and if not supplied the animal soon dies. It is only in this manner that we can ex- 

 plain the different results obtained from similar experiments by Prunelle. No doubt 

 these animals, supposing them to remain lethargic, would ultimately perish when con- 

 fined in an atmosphere deprived of oxygen ; but these experiments at least show that 

 when in a state lethargy they consume exceedingly little oxygen. In this respect they 

 resemble the cold-blooded animals, such as the fishes, frogs, &c., which, it is well 

 known, consume a comparatively small quantity of oxygen; and as we proceed with 

 the enumeration of their physiological peculiarities, w^e shall be surprised to find that 

 they resemble them in almost every particular, affording the strange anomaly of a 

 "-■•"arm-blooded adult mammiferous animal assuming for a time the physiological condi- 

 ■-ton of a cold-blooded animal. There is an experiment mentioned by Prunelle, 

 which, under this point of view, deserves our attention. It is well known that a 

 ■ warm-blooded animal, when confined in a fixed quantity of air, dies before all the 

 exygen is exhausted; while, on the other hand, a cold-blooded animal may breathe for 

 a while with impunity in an atmosphere which cannot support the warm-blooded ani- 

 mal, and rarely dies until all the oxygen is exhausted. Prunelle states that he found 

 all the oxygen had been removed from the air, in which a lethargic animal had been 

 confined until it had proved fatal. Sir A. Carlisle was in error when he affirmed 

 that those animals, in the active state, can subsist with a smaller quantity of oxygen 

 than the other Mammalia. 



We shall now consider the state of the Circulation of the Blood. 

 The circulation, like the respiration, in the state of lethargy appears to be very 

 languid. Prunelle states that the pulsations of the heart of the Bat are 200 per 

 ■minute, in a state of activity, and that they are reduced to 50 or 65, in a state of 

 lethargy. According to the same author, the pulsations of a Marmot, in a state of 

 activity, are 90 in a minute, and are only from 8 to 10 in the minute, and at the 

 same time weak, in the state of lethargy. Marshall Hall found the pulsations of the 

 heart of the Bat 28 in the minute, and regular. The flow of blood in the minuter 

 arteries and veins was slow. Prunelle found the blood in the arteries not florid as it 

 is in a state of activity, but nearly as dark coloured as the blood in the veins, which 

 is exactly what we would expect from the small quantity of oxygen consumed. 

 Eaffon states erroneously that the blood of a hybernating animal, in a state of 

 lethargy, will not coagulate. 



In the reptiles, the movements of the heart are slower and feebler, and the blood 

 is darker coloured, than in t:ie warm-blooded animals. A state of the circulation, 

 . in these respects, which is natural to the cold-blooded animals, would be incompatible 

 with the continuance of life in the warm-blooded animals. During the state of hy- 

 bernation, however, we find the circulation of the blood in these animals to resemble 

 that in the Reptiles. 



"With regard to animal heat, numerous observations show that the temperature of 

 the hybernating animals, during their state of activity, is equal to that of the other 

 Mammalia. On the other hand, while in a state of lethargy, their temperature is 

 little elevated above the surrounding media. 



The heat of the external surface is generally found to be the same as the sur- 

 rounding atmosphere, while the internal parts are from 2" to S*' higher. This is a 

 reduction of temperature from which the other adult warm-blooded animals would 

 never recover. Dr Edwards' experiments go to prove that the temperature of the 

 hybernating animals is more easily reduced, by the apphcation of cold in their state 

 of activity, than in the other Mammalia. Mai'&hall Hall has objected to the accuracy 

 of these experiments. We shall not here stop to inquire into the grounds of his 

 objections. Dr Edv-ards experiments at least prove that their temperature is more 

 easily reduced, under certain circumstances, than the other Mammalia, and that they 



resemble the cold-blooded animals and the young of certain of the Slammalia, which 

 are born with their eyes shut, as the kitten and puppy, in admitting of a great re- 

 duction of temperature with impunity. 



We have already seen that the heart contracts less frequently in a state of lethargy 

 than in a state of activity, and that it cirtTilates dark blood, as in the Reptiles and 

 other cold-blooded animals, and we also find that they resemble them still farther in 

 their tenacity of muscular contractility. It is well known to physiologists that the 

 heart of a Frog, or of a Turtle, or the other muscles of the same animals, will con- 

 tinue to contract, upon the application of a stimulus, for many hours after they havo 

 been decapitated, and are apparently dead, and long after the same parts have lost their 

 contractility in the warm-blooded animals. Mangili observed the heart of a Marm.ot , 

 in a state of lethargy, to beat three hours after decapitation, and after all the principal 

 vessels leading to and from it had been cut through. Upon applying galvanism to the 

 other muscles also, three hours after dwath, he found them to contract vigorously. In a 

 IMarmiOt, killed in a state of activity, the heart was quiescent fifty minutes after deca 

 . pitation. The contractility of the muscles, upon the application of galvanism, was 

 scarcely sensible two hours after death. Marshall Hall has confirmed these observa- 

 tions of Mangili. 



The other vital functions of Secretion, Digestion, Absorption, are also performed 

 in a very languid manner during the state of lethargy, as in the cold-blooded animals. 

 These animals, in a state of lethargy, throw off very little excrementitious matter. 

 Some do not appear to eat during the whole of their hybernation, and others but spa- 

 ringly. The fatness of these animals at the commencement of their hybernation, and 

 their leanness at "its termination, show that absorption must have been going on, 

 though this, of course, is to a much less extent than would have happened had they 

 remained in a state of activity. Mangih found that a Dormouse (Myoxus aveUana- 

 tIus), w^eighing 19 oz. 5 grains, lost 2^ oz. of its weight in three months. V/hen 

 killed it had a considerable quantity of fat around its intestines. Prunelle states tliat 

 two Bats had lost ^^ part of their weight in 21 days. Dr Monro found that a Hedg<?- 

 ■hog, which weighed 13 oz. and 3 drachms on the 25th December, weighed 11 oa. 

 and 7 drachms on the 8th March. This loss was at the rate of 13 grains a-day. 

 According to Mr Cornish, both Bats and Dormice lose from 5 to 7 grains in weight 

 during a fortnight's hybernation. 



The astonishing and unexpected fact, that a warm-blooded adult animal should, 

 w^hen placed under certain circumstances, take on the physiological condition of the 

 cold-blooded animals, naturally leads us to inquire if they have any peculiarity in their 

 anatomical structure which accounts for so interesting a phenomenon. 



Notwithstanding the labours of Mangili, Otto, Sir A. Carlisle, Prunelle, and 

 others, no satisfactory explanation of the cause of hybernation can be derived from 

 the structure of these animals. It will be unnecessary to point out here the pre- 

 tended explanations which some of these celebrated men have advanced, as we would 

 require to enter into minute anatomical descriptions, which would be out of place in 

 an account of this kind. 



We cannot refrain, however, from stating an interesting particular mentioned by 

 Prunelle and Pallas, and that is, that during hybernation the thymus gland becomes 

 much enlarged. Now when we remember that the thymus gland is much larger 

 during the foetal existence than in the adult, and that the fcetus is to a great extent 

 a cold-blooded animal, we have here again another point of resemblance between the 

 hybernating animals, in a state of lethargy, and the cold-blooded animals. 



J. R. 



Speed of the Bull-Frog. — The Bull-Frog {Rana Cateshdana of Shaw) can 

 leap with very great velocity. It is a well known fact, that an American Indian is 

 able to run almost as fast as the best Horse in his swiftest course. In order, there- 

 fore, to try how well the Bull-Frogs could leap, some Swedes laid a wager with a 

 young Indian, that he could not overtake one of them, provided the Frog had two 

 leaps before hand. The wager was accepted, and they carried a Ball-Frog, which 

 they had caught in a pond, into a field, and burned his tail. This application sti- 

 mulated the creature to such a degree, that he made his long leaps across the field 

 with wonderful celerity. The Indian pursued with all his might, and the noise he 

 made in running, added to the fear the poor Frog was probably in of a second burn- 

 ing, made him redouble his efforts, and reached the pond before the Indian could 

 overtake him. 



The Water Spider. — The Insects that frequent the w^ators require predaceous 

 animals to keep them within due limits, as well as those that inhabit the earth, and 

 the Water Spider (^Argyroneta aquatica) is one of the most remarkable upon whom 

 this office is devolved by her Creator. To this end her instinct instructs her to 

 fabricate a kind of Diving-Bell in the bosom of that element. She usually selects 

 still waters for that purpose. Her house is an oval cocoon, filled with air, and lined 

 with silk, from which threads issue in every direction, and are fastened to the sur- 

 rounding plants ; in this cocoon, which is open below, she watches for her prey, and 

 even appears to pass the winter, when she closes the opening. It is most commonly, 

 yet not always, entirely under the water, but its inhabitant has filled it with air for 

 her respiration, which enables her to live in it. She conveys the air to it in the 

 following manner : — She usually swims upon her back, when her abdomen is enveloped 

 in a bubble of air, and appears like a globe of quicksilver. With this she enters her 

 cocoon, and displacing an equal mass of water, again ascends for a second lading, till 

 she has sufficiently filled her house with it, so as to expel all the water. The males 

 construct similar habitations by the same manceuvres. How these little animals can 

 envelop their abdomen with an air-bubble, and retain it till they enter their cells, is 

 still one of Nature's mysteries that have not been explained. We cannot help, how- 

 ever, admiring and adoring the Wisdom, Power, and Goodness manifested in this 

 singular provision, enabling an animal that breathes the atmospheric air to fill her 

 house with it under water; and has instructed her in a secret art, by which she can 

 clothe part of her body with air as with a garment, which she can put off when it 

 answers her purpose Kirby. 



