THE MAMMALIA— MAN AND BEASTS. 



77 



Ucea, and Zoophytes. They seem to depend upon a certain state of the nervous 

 expansion of the retina, when the animal is under the influence of rage, love, hunger, 

 or any violent emotion, especially in the more furious species of Carnivora. This 

 property of the retina is not peouhar to the Blammalia, but is also found among the 

 l\iollusea, Arachnides, and Crustacea. The enormous eyes of certain Cephalopoda, 

 as the Cuttle-fishes (Sepia), appear luminous in the middle of the Ocean, and terrify 

 the Fishes, their prey. The eight, eyes of the Tarantula Spider, a voracious and 

 nocturnal species, are also luminous, according to BI. Leon Dufour. We also find 

 this property among several Saurian Reptiles, such as the genera Anolius and Gecko, 

 whose eyes scintillate in the darkness of night, and the same assertion has been made 

 regarding the Alligators, ^vhich aie thus said to frighten their prey. The ancients 

 have related many fables concerning the piercing looks of the Basilisk Serpents, and 

 modern authors have given credit to the fascinating powers of the Rattlesnake. 

 Certain credulous believers in Animal JMagnetism have also attributed the most ter- 

 ritic effects to the glances of the Toads, and have illustrated their credulity by 

 examples. When carefully considered, these examples only prove a nervous state of 

 the imagination when under the influence of fear. Such eifects may be induced in 

 sensitive frames by the approach of a hideous or dangerous object, and may be ob- 

 served in the lower animals where these involuntary sensations occasion them even to 

 tremble and faint. The effect which the Pointer Dog produces upon the Partridge is 

 a striking instance. But the greatei part of the Carnivora being nocturnal in their 

 habits, such as the Cat genus, as the Lions, Lynx, Ounce; the Dog genus, as the 

 Wolves, Foxes ; the Martens, and probably also the Bats, with the IMocturnal 

 Birds of Prey, have luminous eyes in the dark, whether during the night, or during 

 the day, when confined in a dark chamber. These animals then dilate their pupils, 

 so that ihe expanded surface of the retina at the back of the eye shines vividly, and 

 illuminates the external chamber of that organ. Light is thus projected from within 

 upon those objects on \\hich the anirrial fixes its gaze, that one can distinguish them 

 very well at the distance of more (ban a foot and a half. This emanation appears 

 clearly to proceed from the expanded extremity of the oj'tic nerve. It lasts nearly 

 for a minute at the pleasure of the animal, or even involuntarily when under the in- 

 fluence of viole ".t emotions. Certam Apes, as the Socthora trivirgatay and the How- 

 lers (Mt/cetcs), have nocturnal eyes possessed of this radiatinij; property. Inflamma- 

 tion, in various diseases of the liye, gives to some BJcn a temporary power of seeing 

 in the dark, or of emitting luminous rays. The eye when rubbed, or when it 

 receives a blow, becomes dazzled by the sudden influx of blood into this organ, and 

 not only do scintdlations appear, but there is a luminous emission when these 

 animals are enraged, like that proceeding from an electrical discharge. 



The luminosity of the retina does not proceed from a simple reflection of those 

 scattered rays of Light which may chance to fall upon the Eye, as Treviranus and 

 Benj. Prevost have considered probable, for these phenomena can be observed in the 

 most perfect darkness. The Cat, when irritated, darls forth fiery rays of light; its 

 eyes sparkle intermittently wlic^n enraged, according to Esser and Rengger; and 

 Gruithuisen remarked ihat the rays acquired a greenish tinge when the animal was 

 caressed, Dops, when enraged, impart to their ocular rr!diatic;ns a tinge sometimes 

 yellowish and sometimes blueish. Their corruscations vaiy with individuals, but the 

 luminous emanations appear to be most brilliant in animals with black or ash-coloured 

 hair. They neither proceed from the crystalline nor vitreous humours of the Eye, 

 for these can be altogether removed without destroying their luminous proptrty, 

 . -which only then acquires a more greenish hue. But on wounding the optic nerve, 

 or on scraping the retina, the radiation becomes exinict; thus proving that it pro- 

 ceeds neither from the cornea or uvea, or indeed from any of the transparent portions 

 of the Eye. 



GENERAL REVIEW OF THE MAMMALIA CONTINUED. 



Phenomena of Sleep — the Hyheniation of some Species. 



The phenomena of Sleep bear an immediate relation to the most general laws of Na- 

 ture, and form an important illustiiition of the fact, that the periodical motions of the 

 animal economy are in direct correspondence with the movements of our planetary 

 system, and especially with our situation relative to that Sun which regulates the pe- 

 riods of the day and year. ** All our wants reappear," says Cabanis (Rapports du 

 Physique et du Moral de THomme), "and all our functions execute themselves, in 

 fixed and iso-chronous periods. The duration of the functions is the same in each 



. period ; the same appetites or the same wants have the hours marked for their return ; 

 and it commonly happens, when these wants are not immediately satisfied, they dimi- 

 nish and disappear ior a certain time, only to return again with the greater force and 

 importunity at the next succeeding period, which ought to produce a return of the 

 impression. This character of periodicity is particularly remarkable in the returns 

 and duration of sleep, which commonly reappears during each astronomical day at the 

 same hour ; continues nearly for the same period of lime ; and according as it is re- 

 gular in its periods, siumter is the more easy, while the repose which follows is the 

 more salutary and refreshing." 



There are two piincipal states of vital activity, of which all animals partake in dif- 

 ferent degrees. When the vital excitement exists to its full extent, the animal is 

 said to be uwuke ; when the functions of life arc suspended, either wholly or partially, 

 it is said to be aUetp. From this waking state, when life exists in all its plenitude, 

 there may be many degrees of its dimmution, called Reverie, Deliiuaiiy Breaming, 

 Sleep, 2'urpcr, Sivpor, Asphyxia, Lethargy^ according to their mtensity, of which 

 states the last is but one degree removed from absolute death. 



The principal occasions on which these states of vital repose naturally present them- 



. selves to our observation are, Ut, When the body and mind of an animal languish 

 either from the return of their period of natural repose, or through excessive exer- 

 tion. 2d, When the cold of winter, or ptrhaps also the heat of summer, acting on 

 special constitutions, suspends the animal functions of life either partially or entirely. 

 The former phenomenon appears daily, while the latter is of annual recurrence. 



The first of these occasions, or Sleep properly so called, differs from Death, with 

 which it has often been compared, in the circumstance that all the involuntary 

 20 



functions of life continue their action uninterruptedly. It may be recollected that 

 animals have two kinds of vital functions; the one vegetative and internal, which . 

 continue, with the exception of generation, to exert themselves during the entire 

 existence of each individual, and the other purely animal, which refer to external ob- 

 jects. The former being essential to their existence, are never suspended ; the latter 

 are intermittent in their action. If the heart ceased to propel the blood through the 

 arteries, if the lungs ceased to respire air, if the functions of nutrition and secretion 

 were discontinued, or if they depended upon the mere Will of the animal, life would 

 soon become extinct. But all these internal actions are involuntary, and hence it is 

 only the external and purely animal functions of life which can have their periods of 

 action and repose, of waking and sleeping. These latter actions are therefore less essen- 

 tial to life than the former. An animal, when profoundly asleep, is reduced to a state very 

 analogous to that of a plant. Though dormant, he is still a living beino-, for he con- 

 tinues to perform the functions of nutrition and secretion even mure perfectly than 

 when awake ; but he is destitute both of sensation and motion, and must awake be- 

 fore he can fully resume these functions peculiar to anim-als. Thus animals have two 

 states of existence, waking and sleeping, while a plant has only one. The state of tho 

 latter may, however, be more or less active, according to the difi'erent degrees of heat 

 or light to which it is exposed. There can be no diiiorence with plants between tho 

 activity of the internal and external functions, and they always appear to be plun^-ed 

 in a state of repose more or less profound. Many of the lower animals, such as an 

 Oyster or a Zoophyte, when considered superficially, appear to exist in a continued 

 state of torpor, rather than to possess an active life, because they maintain but few 

 relations to external objccis, and hence are commonly considered rather as vcTetatinw 

 than as living, although Plants are possessed of life as well as animals, but only in 

 different degrees. 



Sleep, in fact, consists in the suspension of the organs of sense and voluntary 

 motion, qualities which chiefly serve to distinguish animals from plants. All the vo- 

 luntary muscles repose completely, and the sleeping animal maintains no active rela- 

 tions with external objects. The functions belonging to vegetable life continue their 

 existence, but the consciousness of existence is lost. The heart and the Itin'^'s con- 

 tinue to act without interruption, while the organs of thought and sensation possess 

 but d temporary action. It is thus precisely those, organs which are the most inti- 

 mately connected with the Mind, namely, the organ? of thought and sensation, which 

 most require repose, and the human Soul, though immortal, when entirely separated 

 from the Body, cannot now maintain its consciousness uninterruptedly for twenty-four 

 hours together. 



Ni^ht, or the absence of light, is favorable to the sleep of all animals not natu- 

 rally of nocturnal habits. Silence, repose, the absence of noise, and in general every 

 thing which interrupts the relations of the animal with external objects, are favorable 

 to sleep. As long as the purely animal functions continue to be stimulated, they 

 maintain their action, until an excess of action profJuv.es a contrary effect. A violent 

 exertion of the body, profound thought, or any powerful sensation, disposes for sleep. 

 0;'ten the fatigue of a single sense brings on the sleep of all the senses, through that 

 intimate connexion maintained among all the parts of the body. The monotonous 

 murmurs of a brook, the howling of a forest, bad music, protracted readino-^ bad 

 verses, or a long lecture on an uninteresting subject, gradually fatigue the sense of 

 hearing or sight, and lead the vital forces of these organs to seek in sleep for an 

 accession of energy, and the repose of the entire animal functions speedily follovps. 



The inclination to Sleep is announced by a slowness of motion, by languor of the 

 Attention and Will, and by the gradual stupefaction of the senses. But the difl^erent 

 kinds of functions are suspendetl in a certain order of succession, according to their 

 nature and relative importance. The muscles which move the arms and legs are 

 relaxed and cease to act before those which sustain tho head, and the latter before those 

 which support the spine. When the sense of si;:;ht is first suspended by the fallinf^ of 

 the eyelids, the other senses still maintain their action. The sense of Smelling is obli- 

 terated before the taste ; Hearing after smelling ; and Touch last of all. Even during the 

 most profound sleep, the sense of touch continues to suggest difl'erent movements and 

 changes of position, when the long duration of the same posture renders it disa<:n*eeable. 

 At length animal exertion is at an end; the muscles, excepting those of Circulation and 

 Respiration, cease to act; and the body sinks down, obedient to the ever-actin"- force 

 of Gravitation. 



These phenomena of Sleep are very analogous to that insensibility of particular 

 organs, during our waking moments, when the Attention is fully engaged. A pro- 

 found Biathematician, when absorbed in a calculation, neither sees, hears, nor feels ; 

 all the functions are asleep except the organ of thought. Other Men, like mere 

 machines moved by habit, perform the same operation a thousand times with their 

 hands, whi.e the thinking principle remains buried in a profound lethargy. 



At the precise moment when the Mind loses its consciousness, there results a ge- 

 neral relaxation of all the muscles. If the body be at rest and in health, this sudden 

 change in its state of obedience to the Will is attended with no marked result. Bui 

 if the body be fatigued, or in an uneasy posture, or if the joints or muscles be paii>- 

 ful, this first result of Sleep has the effect of removing it entirely. Hence arises the 

 dilBcaity of sleeping in a sitting posture, or during an attack of .gout or rheumatism . 

 The pain which the sudden startmg of the muscles occasions is often so great in 

 these diseases, that Sleep can only be induced by strong doses of opium or some 

 other narcotic. It also follows from this relaxation of tho muscles, that th« limbs 

 become bent during Sleep, and that a substance grasped firmly in the hand, falls at 

 the instant when consciousness is lost. 



During Sleep the character of the Respiration is altered; it becomes less frequent 

 and deeper. The heart also beats more slowly, but the pulse is stronger. The 

 Heat of the surrounding air, when imperfectly- renewed, tends, however, to increase 

 its movements. 



The heat of the body is not naturally higher during Sleep ; on the contrary, a 

 diminished respiration tends to lower the tempera'ure. It usually happens, however, 

 from external circumstances, that there is an apparent rise of temperature, from tha 

 body being surrounded by imperfect conductors of heat, and from the circumambient 

 air being but slowly renewed. 



