78 



FIRST CLASS OF THE VERTEBRATED ANIMALS. 



As the stomach is a muscular orjan, and as the passage of the food through the 

 pylorus depends upon the rapidity with which the almost insensible contractions of the 

 Stomach are performed, it follows that Sleep retards digestion, while, at the same 

 time, it renders it more complete. This slowness of digestion is further increased by 

 the state of rest in which the body remains, as nothing tend^ more to excite a rapid 

 dif^estion than the gentle motion of the limbs, or of the entire body. The same 

 phenomena take place in the intestines, where the aliments remain almost inert in 

 the several portions of the alimentary canal. However, the slowness of this movement 

 favors the formation of chyle, and renders its absorption more (complete. 



Absorption is very active during Sleep, and the danger of slumbering in noxious 

 air hence becomes very great. Travellers are usually advised to avoid sleeping in 

 marshy situations, such as the Pontine IMarshes of Italy, especially in the warm sea- 

 son of the year. Perspiration also is performed more easily, because the pores remam 

 open during the state of muscular relaxation. " Una nutrition plus efficace, la re- 

 paration graduelle des forces qui en resulte, et aussi la repletion de la vessie, toutes 

 ces choses reveillent en nous, durant le sommeil, des idees de jouissance et des sou- 

 venirs de volupte.' 



As all the senses do not fall asleep at the same time, so they differ in the order in 

 ■which they awake. Taste and Smell commonly resume their functions last of all. 

 The sense of Sight is roused with greater difficulty than that of Hearing. An un- 

 expected noise will often awaken a Somnambulist from his lethargy, upon whom the 

 strongest rays of light will have had no previous effect, although his eyes continue 

 open. Touch, as it was the last sense to become dormant, so it appears to be the 

 most easily roused. The same person who cannot be awakened by very loud 

 noises, will rise instantly on being gently tickled on the soles of the feet. Often the 

 mere approach of the respiration of another will be sufficient to rouse the soundest 

 sleeper. 



The positions which the Jlammalla assume during Sleep are very various. The 

 young animal sleeps with its limbs gathered together, in a posture most resembling 

 that of the fcetus in the womb. This situation is very favorable to the renewal of 

 the animal forces, by permitting the relaxation of all the articulations, and in preserving 

 the heat of the more sensitive parts. For the latter reason, the Dog and Cat sleep 

 vi'ith, their bodies formed into a circle. Some Mammalia sleep in the open air, while 

 other--, retire to caves and sheltered places. Many repose without any covering, 

 while others prepare a bed of some imperfectly-conducting substance, to preserve the 

 temperature of their bodies, which would otherwise fall during Sleep below the na- 

 tural standard. It is usually on the right side that Man reposes. This posture 

 favors the action both of the heart and stomach, as the vibrations of the former 

 would reverberate through the body from the reaction of the substance upon which 

 it reposes, and the latter would be compressed by the weight of the liver. After 

 sleep, all the organs, being refreshed, repaired, and completely nourished, acquire a 

 greater size ; thus I\Ian and other animals which commonly hold the spine more or 

 less erect, are taller in the morning than in the evening after the fatigues of the 

 day. 



Sleep is not always profound ; some of the animal functions continue to act ; ideas 

 succeed each other, and the animal is said to dream. The power of dreaming is 

 falsely ascribed to Man alone ; other Mammalia dream likewise, because they are 

 capable of thought, and possess a certain degree of intelligence. Sometimes the Do-^ 

 is observed to howl, struggle, and perspire copiously, flloving his tail snd limbs 

 rapidly, he pursues the Hare in imagination, and, on the point of seizing it, closes his 

 teeth and lips as if in the act of dyeing them in blood. Some Birds are also known 

 to dream, as the Parrots. Those animals which are most easily excited dream more 

 frequently than the others ; thus the Horse is more liable to dream than the Bull. 

 According to Chabert, this phenomenon among Cattle is observed only in the Bull, 

 the Ram, or in Cows which are suckling. 



It is possible to protract the usual period of sleep by an unusual excitement ; but if 

 the stimulus be long continued its effect goes off, and then nothing can prevent sleep 

 as long as the health coiitinues good. In fact, sleep, once in the twenty-four hours, 

 is as essential to the existence of the Mammalia as the momentary respiration of fresh 

 air. The most unfavorable conditions for sleep cannot prevent its approach. 

 Coachmen slumber on their coaches and couriers on their horses, while soldiers fall 

 asleep on the field of battle, amidst all the noise of artillery and the tumult of war. 

 During the retreat of Sir John Moore, several of the British soldiers were reported 

 to have fallen asleep upon the march, and yet they continued walking onwards. The 

 most violent passions and excitement of the mind cannot preserve even powerful 

 minds from sleep; thus Alexander the Great slept on the field of Arbela, and Napo- 

 leon upon that of Austerhtz. Even stripes and torture cannot keep off sleep, as cri. 

 minals have been known to slumber on the rack. Noises which serve at first to drive 

 away sleep, soon become indispensable to its existence ; thus a stage-coach stopping 

 to change horses, wakes all the passengers. The proprietor of an iron forge, who 

 slept close to the din of hammers, forges, and blast furnaces, would awake if there 

 was any interruption to them during the night ; and a sick miller, who had his mill 

 stopped on this account, passed sleepless nights until the mill resumed its usual 

 noise. Homer, in the Iliad, elegantly represents sleep as overcoming all men, and 

 even the gods, excepting Jupiter alone. 



The length of time passed in sleep is not the same for all men ; it varies in dif- 

 ferent individuals and at different ages ; but nothing can be determined from the time 

 past in sleep, relative to the strength or energy of the functions of the body or mind. 

 From six to nine hours is the average proportion, yet the Roman Emperor Caligula 

 slept only three hours. Frederic of Prussia and Dr John Hunter consumed only 

 four or five hours in repose ; while the great Scipio slept during eight. A rich and 

 lazy citizen will slumber from ten to twelve hours daily. It is during infancy that 

 sleep is longest and most profound. "Women a!so sleep lon;^er than men, and young 

 men longer than old. Sleep is driven away during convalescence after a long sick- 

 ness, by a continued fasting, and the abuse of coffee. The sleepless nights of old 

 age are almost proverbial. It would appear that carnivorous animals sleep in gene- 

 ral longer than the herbivorous, as the sup.-rior, activity of the muscles and senses of 

 ^he former seem more especially to require repair. Satiated ^vith their prey, they 



V- 



are obliged to seek repose to digest those very substantial matters which compose 

 their aliment. 



In general, it may be stated, that during sleep the internal functions predominate 

 over those relating to the exterior of the body. Every thing which tends to inter- 

 rupt the relations of the external with surrounding objects serves to induce sleep. 

 On the contrary, the existence of external stimuli tend to expel it, until at length 

 they lose their effect by long-continued exercise. 



From this it ought to follow that excessive cold, which benumbs the external 

 powers, ought to occasion sleep. When exposed to the aetion of a low temperature, 

 animals experience an irresistible desire to sleep, which soon terminates in death. 

 Of this there are frequent examples in the inhospitable climates of the north, Sibe- 

 ria, Lapland, and Kamschatka, or on the tops of high mountains, as the glaciers of 

 Switzerland. Dr Solander and party nearly lost their lives from this cause among 

 the hills of Terra del Fuego. Surprised by an excessive cold, he was with difficulty 

 prevented by his companions from yielding to this impulse of nature, although know- 

 ing well the consequences of sleeping. — (See Captain Cook's First Voyage). Tra- 

 vellers on horseback are peculiarly liable to be overcome by this propensity to sleep, 

 when the cold is very intense, in which case they are sure to be frozen to death. 



There prevails among many Mammalia a singular internal modification, which can- 

 not be explained by any cause more general than itself, but must be referred to some 

 unknown original constitution. We refer to that state of torpidity commonly called 

 Hybernation, into which some animals fall during a part of the autumn and in win- 

 ter, but from which they escape early in spring. Although %ve are wholly ignorant 

 of the cause of this v.inter sleep, the effects and design are well known. It seemn 

 obviously intended to preserve the animals in situations where they could not have 

 maintained their existence, from the impossibility of finding an adequate supply of 

 food. Accordingly, all the active functions of life are suspended, where their exer- 

 cise would be incompatible with more general laws. 



At a more or less advanced period of the autumn, depending on the denree in 

 which the temperature is lowered, animals possessed of this peculiar coniititution seek 

 to shelter themselves from the cold and wind, by retiring into holes excavated in the 

 ground, walls, trees, or among the bushes. These retreats they line carefully with 

 grass, green leaves, moss, and other bad conductors of heat. Hybernation occurs 

 among several of the Mammalia, as in the Fat Dormouse (^Mi/oxus gUs)^ the Garden 

 Dormouse (il/. niiela), the Common Dormouse (M. avellanarius) , the Hedgehog 

 (^Erinaccus Europama)^ the Bats, the Alpine Blarmot (^Arctomys marmota), the 

 Hamster (Cricetus vulgaris^^ the Jumping Mouse of Canada (Menones nemoralis^y 

 and some others. Animals with cold blood hybernate as well as some of the Mam- 

 malia. Many Reptiles become torpid in cold climates, as well as some Insects, Mol- 

 lusca, and Worms ; but in general the degree of their lethargy is much less profound 

 than that of the hybernating Jlammalia. They pass their time of hybernation with- 

 out food, but are not always deprived of sensation and motion, even at the freezing 

 point. 



" It is highly important," observes Dr Marshall Hall, *' to distinguish that kind 

 of torpor which may be produced by cold in any animal from true hybernation, which 

 is a property peculiar to a few species. The former is attended by a benumbed state of 

 the sentient nerves, and a stiffened condition of the muscles ; it is the direct and im- 

 mediate effect of cold, and even in the hybernating animal is of an injurious and fatal 

 tendency; in the latter, the sensibility and motility are unimpaired, the phenomena 

 are produced through the medium of sleep, and the effect and object are the preser- 

 vation of life. Striking as these differences are, it is certain that the distinction has 

 not always been made. In all the experiments which have been made with artificial 

 temperatures especially, it is obvious that this distinction has been neglected. Tnre 

 hybernation is induced by temperatures only moderately low. All hybernating ani- 

 mals avoid exposure to extreme cold. They seek some secure retreat, make 

 themselves nests or burrows, or congregate in clusters ; and if the season prove un- 

 usually severe, or if their retreat be not well chosen, and they be exposed, in conse- 

 quence, to excessive cold, many become benumbed, stiffen, and die. To induce true 

 hybernation it is quite necessary to avoid extreme cold, otherwise we produce the 

 benumbed and stiffened condition to which the true torpor or torpidity may be ap- 

 propriated. I have even observed that methods which secure moderation in temper- 

 ature lead to hybernation. Hedgehogs supplied with hay or straw, and Dormice 

 supplied with cotton wool, make themselves nests, and become lethargic; when other?, 

 to which these materials are denied, and which are consequently more exposed to cold, 

 remain in a state of activity. In these cases warmth, or moderate cold, actually con- 

 cur to produce hybernation." 



The kind of retreat which each animal prepares varies with the species. Tlie 

 Bats, besides hybernating in holes, also hang suspended in grottoes and caverns, 

 where the temperature is milder than in the open air. Other hybernating animals 

 are satisfied with bringing their head nearer to their lower extremities, so as to pro- 

 sent a surface of less extent to the cold. On discovering them in their retreats, 

 they are found rolled up, cold to the touch, motionless, stiff, their eyes closed, their 

 respiration slow, interrupted, scarcely perceptible, or none at all. Their insensibility 

 is sometimes such that they may be moved, rolled about, and shaken in every possibls 

 way, without being disturbed from their torpor. 



During the spring or summer, when these animals enjoy their full activity, they 

 possess an elevated temperature, which may vary according to the species and indi- 

 viduals, between 95^* and 98^" Fahrenheit, and consequently is between those limits 

 which characterize the animals with wai-m blood. When examined in the autumn, 

 with the viev/ of ascertaining the changes which they then undergo, it is observed 

 that their temperature falls rapidly as the cold season advances. Their respiration 

 gradually becomes impeded, their movements are less rapid, and their appetite di- 

 minishes ; but these animals still mamtain the use of their senses and the power of 

 locomotion. This intermediate state, between the full possession of life in all its vi- 

 gour, and absolute torpidity, may continue for one or two months. 



The degree of external temperature at which they become absolutely torpid va- 

 ries with the species, and even according to the individual. In general, the disposi- 

 tion to byberucite follows in 3 descending scale of temperature, of which the follow- 



