i:n;ns. 



BIRDS. 



vary much in different specie* and even in the sexes, particularly 

 among the water-birds. In the domestic or dumb swan the windpi|>e 

 U straight ; in the male wild swan the windpipe is convoluted in the 

 hollow of the breast-bone, like the tube of a French horn. 



The following are the conclusions of M. Jacquemiu from hi* observa- 

 tions on the respiration of birds. After observing that the air enters 

 not only into the lungs and about the pariete* of the chest, but that 

 it also penetrates by certain openings (foramina) into eight pneumatic 

 ban or air-cells, occupying a considerable portion of the pectoro- 

 abdominal cavity, and thence into the upper and lower extremities, 

 be concludes : 1st, That the pneumatic bags are so situated as to be 

 ready conductors of the air into the more solid parts of the body ; 

 and that the air, by surrounding the most weighty viscera, may sup- 

 port the bird in flight, and contribute to the facility of its motions 

 when so employed. 2nd, That the quantity of air thus introduced 

 penetrates the most internal recesses of their bodies, tending to dry 

 the marrow in the bones and a portion of the fluids ; a dimiuuti. .n >>f 

 specific gravity is the result, the true cause of which has been, in 

 his opinion, vainly sought in the quantity alone of permeating air. 

 3rd, That in birds the oxidation of the nourishing juices is not entirely 

 effected in the lungs, but is much promoted also in the pneumatic 

 bags above mentioned, for their contained air operates through the 

 membranes upon the blood-vessels and lymphatics in contact with 

 them ; a more complete and speedy oxidation is the result. 4th, That 

 not only the skeleton, but all the viscera are much more permeable 

 by air in birds than in any of the other vertebrated animals. 5th, That 

 the air-reservoirs are not always symmetrical, their shape and extent 

 depending entirely upon the form and situation of the organs among 

 which they occur ; but the supply is so modified that the total quantity 

 received into the pneumatic bags on the right side of the body is equal 

 to that which enters into those on the left ; and indeed without the 

 maintenance of this condition the act of flying would be impossible, 

 and that of walking difficult. 6th, That no portion of a bird's struc- 

 ture U impervious to air ; it reaches even the last joints (phalanges) 

 of the wings and feet, and the last caudal vertebrae, or rump-bones. 

 The quill of the feathers is not excepted, as has been sometimes 

 asserted. 7th, That the air within the head has a separate circulation, 

 anil does not directly communicate with the air-pipes of the rest of 

 the body. 8th, That in no instance does the air come into direct 

 contact with the viscera or nourishing juices, but invariably through 

 the medium of a membrane, however fine and transparent. 9th, That 

 the volume of air which birds can thus introduce into their bodies, 

 and the force with which they can expel it, offer the only explanation 

 how so small a creature as a singing-bird (the nightingale, for example) 

 is able to utter notes so powerful, and without any apparent fatigue 

 to warble so long and so musically. 



The organs of respiration in birds, as well as their sexual organs, 

 are, according to Purkinje and Valentin, supplied with cilia on their 

 surface. 



Brain, Nervout Syttem, and Sentet. 



The brain of birds possesses the same characters which are to be 

 found in other oviparous vertebrated animals, but its proportional 

 volume is its distinguishing peculiarity ; and this volume often sur- 

 passes the development of that organ in mammifers. Indeed, in some 

 birds, and more particularly in some of the songsters, the brain has 

 been said to exceed that of man when considered in reference to the 

 size of the head and of the whole body. The following scale has been 

 given as an example of the size of the brain in relation to that of the 

 body: Eagle, l-2tiftth of the body; sparrow, l-25th; chaffinch, 

 l-27th; redbreast, l-32nd; blackbird, l-68th; canarybird, l-14th; 

 cock, 1 -25th ; duck, l-257th ; goose, l-360th. In man the brain forms 

 from l-22nd to l-33rd of the body; in some apes, l-22nd; in the 

 elephant, l-500th ; in the horse, l-400th ; in the dog, l-101st; and in 

 the cat, l-04th. 



The size of the brain in birds arises principally from tubercles 

 analogous to the corpora striata of mammifers, nml not from the 

 hemisphere!!, which are small, smooth, and without convolutions. 

 The cerebellum is large, almost without lateral lobes, and formed 

 principally by the vermiform process. Several parts found in the 

 brain of mammifcrs are absent in birds, and among these are the 

 corpus callosum and pans Varolii. 



of the five sense*, sight, smell, and hearing are most acute 

 in birds. 



>V'/AA We have seen that the bony orbits ore of great magnitude, 

 and the organs of sight which are contained therein are proportionately 

 large. In the birds of prey the orbits have the shape of a "ohalioe, 

 says Dlumenbach, "or cup used in the communion service. The 

 cornea, which is very convex, forms the bottom of the cup, and the 

 posterior segment of the sclerotica resembles its cover. This peculiar 

 form arises from the curvature and length of the bony plates, which, 

 as in all other birds, occupy the front of the sclerotica, lying close 

 together and overlapping each other. These bony plates form in 

 general a flat or slightly convex ring; being long and curved in the 

 J fijiitret (Hawks) they form a concave ring, which gives the wh'ile 

 eyeball the above-mentioned form." By means of this ring the eye 

 becomes a kind of self-adjusting telescope, so M to take in both near 

 and very distant object*. 



A representation of the sclerotic plates, forming the bony ring in 



the eye of the Penguin (Aptaiodytei), is here given. They remind 

 us forcibly of the eye-plates in some of the reptiles, particularly of 

 those belonging to the eyes of the Enaliouurians, or fossil marine 



lizards. The penguin has to 

 mljust its eye for vision l>tli 

 on laud and under water. Thin 

 contrivance must greatly assist 

 the adjustment necessary for 

 seeing clearly in such different 



' The crystalline humour is 

 flat in birds ; and 

 humour is very small. 

 Sclerotic Plates of Penguin (Apttnodyta). colour of the iris varies in 



different species, and in many 



cases is very brilliant. The marsupium, which arisen in the back 

 of the eye, and the use of which is not very clearly ascertained, 

 ifl a peculiarity in the eye of birds. They have three eye-lids, two of 

 which, the upper and lower, are closed in most of the race by the 

 elevation of the lower one, as may be frequently seen in our domestic 

 poultry. The owl, the goat-sucker, and a few others, have the power 

 of depressing the upper eye-lid. Of these birds the upper only in 

 furnished with eye-lashes generally; the oetridh, secretary vulture, 

 some parrots, and a few other birds, have them in both lids, liut 

 the third eye-lid, or nictitating membrane, forms the most curious 

 apparatus. When at rest, this, which is a thin semi-transparent fold 

 of the tunica conjunctiva, lies in the inner corner of the rye. with 

 its loose edge nearly vertical. By the combined action of two muscles 

 which are attached towards the back of the sclerotica, it is capable of 

 being drawn out so as to cover the whole front of the eye-ball like 

 a curtain, and its own elasticity restores it to the corner in which it 

 rested. This, it is said, enables the eagle to look at the nun. The 

 peculiar movements of this organ may be seen amongst the fine 

 collection of eagles at the gardens of the Zoological Society in the 

 Regent's Park. 



Hearing. This sense appears to be sufficiently acute in birds, though 

 (with the exception of the night-birds, the owls in particular) they 

 have no external cartilaginous ear; and the peculiar valve, partly 

 muscular, partly membranous, placed at the auditory opening even 

 in those birds, has none of the development which generally mark* 

 the concha of mammifera. The peculiar arrangement of the compara- 

 tively loosely barbed feathers, however, round the aperture (in 

 audit-orius) compensates for it; and this arrangement may be well 

 seen in the rapacious birds. The membrane of the drum (membrana 

 tymponi) is convex externally, and the drums of both ears are 

 connected by the air-cells of the skull. There is neither malleus nor 

 stapes, and their place is supplied by a single auditory bone 

 culum auditus) which connects the membranes of the drum with the 

 fenestra ovalis. The Kustachian tubes terminate in a sort of common 

 aperture on the concavity of the palate. The labyrinth in without a 

 cochlea ; instead of which there is a short, blunt, hollow bony process 

 obliquely directed backwards from the vestibule, and divided into 

 two portions", one of which ends at the fenestra rotunda. 



fin: II. This sense in the majority of birds seems to be highly 

 developed. The olfactory nerve is given off from the foremost ]irt 

 of the front lobe of the brain, whence it passes along a canal i 

 nose, and is ramified on the pituitary membrane, which is 

 over two or three pairs of bony or cartilaginous concha; narium. The 

 nostrils terminate in different ports of the upper mandib].- in 

 different genera; and, according as these apertures are sniaM 

 larger, or more or less covered by membranes, cartilages, feathers, or 

 other integument*, the sense is probably more or less acute, lint no 

 bird is without nostrils, though Button asserts that several are 

 unprovided with them : the pufiin indeed and some others have 

 them so small, and placed so closely on the margin of the inaudible, 

 that they are not cosily deter 



This sense was supposed to have reached its highest point of 

 perfection in the vultures and other carrion-bii .! I' >- and philo- 

 sophers have dwelt on the 'delight' with which they 

 " ..... snutTil the smell 

 OI ni'.it:il r!i;mi:<- on earth . 

 Sagacious of the quarry from afar." 



But, according to the experiments of Audubon (and they wen 

 with a species which has obtained a reputation for great sagacity in 

 this way), the nostrils do not seem to have been of the least. 

 ance to the birds in directing them to their prey; while tli 

 even when the I'irds were for above human si^ht. appears I 



I'allil.le. Tliis conclusion has lcen indeed disputed: but tho 

 facts stated I iv Audubon are very strong. 



Trulf.- -Though all birds jmssess a tongue, it is probable that but 

 few find enjoyment in the organ as ministering to their t,-i ' 

 in those it is soft, thick, and covered \vitli papill of the 



birds rif prey, some of the swimmer.-, and the parrot^ generally, have 

 sueh a ! there ean l>e no doubt that these taste i'ood of a 



soft or tluid nature, and select, that whieh they like 1., ~\, liut in 



(lie tongue is horny and still', and appears imsuitcd to < 

 sueh ii though as an organ for diking food it bee. ] 



the highest importance. In the humming-birds and other li- 



