B I R 



427 



I R 



lege of Surgeons (London) is a large glass bottle entirely 

 filled with pebbles, &e. taken from the stomach of an 

 ostrich. The well-known experiments of conveying bullets 

 beset with needles and even lancets into the stomachs of 

 granivorous birds, with the effect of the total destruction of 

 those sharp instruments in a short period, need only be re- 

 ferred to here ; but as Felix Plater's observations have not 

 attained quite so much celebrity, we shall shortly mention 

 them. He found that an onyx swallowed by a hen was 

 diminished one-fourth in four days, and that a louis d'or 

 lost in this way sixteen grains of its weight. 



In such birds as nourish their young from the crop the 

 glands swell very much at the hatching season, and secrete 

 a greater quantity of fluid than usual. In the pigeon, 

 which thus feeds its young, there is a spherical bag formed 

 on each side of the oesophagus, a specimen of which may be 

 seen in the museum of the College of Surgeons. It is not 

 improbable that the banter about ' pigeon's milk' took its 

 rise from this part of the (Economy of the bird. 

 . In those birds which feed on flesh, fish, or worms, and 

 which consequently do not require so powerful an apparatus, 

 the muscles of the gizzard are reduced to an extreme 

 weakness, and that organ appears to make only a part of 

 the same membranous bag with the ventricule succenturie. 



The food being thus reduced into a sort of chyme, passes 

 through the remainder of the intestinal canal, where all the 

 nutritious parts are taken into the system, and the remainder 

 is at length expelled by the cloaca, where the urinary ducts 

 terminate, and the organs of generation are situated. It 

 may be worth mentioning that the liver becomes much 

 larger in domesticated birds than in wild ones (a propen- 

 sity which can be increased by artificial means, as the 

 gourmand who revels in his foies grog well knows), and 

 that the gall-bladder is entirely wanting in some birds, the 

 parrot and pigeon for instance. Hence, no doubt, the 

 saying, ' He has no more gall than a pigeon.' The pan- 

 creas (sweet-bread) is of considerable size in birds, but the 

 spleen is small. 



Vital Functions and Organs of the Voice. 



The heart, in this class, is of peculiar structure. Instead 

 of the membranous valve which is present in both ventricles 

 of the heart of mammifers, and in the left ventricle in birds, 

 the right ventricle of the heart in the latter is furnished with 

 a strong muscle which assists in driving the blood with greater 

 impetuosity from the right side of the heart into the lungs ; 

 a structure rendered necessary from the want of expansion 

 of ihe lungs in breathing consequent upon their connexion 

 with the numerous air-cells. The lungs are small and 

 flattened, and adhere to the back of the chest in the inter- 

 vals of the ribs, and a considerable part of the abdomen as 

 well as of the chest is occupied by membranous air-cells 

 with which the lungs communicate by considerable aper- 

 tures. In addition to these, a great portion of the skeleton 

 in most birds becomes a receptacle for air. Instead of mar- 

 row the larger cylindrical bones contain air, and form large 

 tubes, interrupted only towards the ends by transverse bony 

 fibres. The broad bones present internally a reticulated 

 bony texture, pervaded by the same fluid, communicated 

 from the lungs by small air-cells. The enormous bills of 

 the toucan and of the hornbill are supplied with air from 

 the same quarter. The very barrels of the quills, when 

 fully developed, can be filled with air or emptied at 

 the pleasure of the bird ; and it is thus that the voluntary 

 erection of the plumage in the turkey, &c., is supposed to 

 be in great measure produced. 



The effect of this structure in lightening the body of the 

 bird, and facilitating its motions whether in flying, swim- 

 ming, or running, is obvious. Where the demand is greatest 

 (as in birds of the highest and most rapid flight) the supply 

 is largest. Thus, in the eagle, we find the bony cells of 

 great size, and very numerous. The section of a head of 

 tlie hornbill (Bucerns Rhinoceros), here represented, will 

 convey some idea of the structure of these air-cells. 



The organs of the voice in birds bear a striking resem- 

 blance to certain musical wind-instruments. The larynx is 

 double, or rather made up of two parts : one, the proper 

 rimti glnftidis, situated at the upper end of the windpipe ; 

 and tne second, the bronchial, or lower larynx, which con- 

 t.iius a second rima glottidis, furnished with tense mem- 

 branes that perform in many birds (and especially in the 

 aquatics) the same part as a reed does in a clarionet or 



hautboy, while the upper rima, like the ventage or hole of 

 the instrument, gives utterance to the note. 



[Section of the head of Buceros .RAraoc,)j.j 



The length of the windpipe and the structure of the lower 

 larynx vary much in different species and even in the sexes, 

 particularly among the water-birds. In the domestic or 

 dumb swan the windpipe is 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. Jacquemin in his 

 paper lately read before the French Academy ; and though 

 many of the facts were previously known, M. Jacquemin's 

 communication must be considered as a valuable addition to 

 this part of the subject. After observing that the air enters 

 not only into the lungs and about the parietes of the chest, 

 but that it also penetrates by certain openings (foramina) 

 into eight pneumatic bags or air-cells, occupying a consi- 

 derable portion of the pectoro-abdominal cavity, and thence 

 into the upper and lower extremities, he 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 support 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 diminution of 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 con- 

 tained air operates through the membranes upon the blood- 

 vessels and lymphatics in contact with them ; a more com- 

 plete and speedy oxidation is the result. 4th. That not 

 only the skeleton, but all the viscera are much more per- 

 meable by air in birds than in any of the other vertebrated 

 animals. 5th. That the air-reservoirs are not always sym- 

 metrical, 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 diffi 

 cult. 6th. That no portion of a bird's structure is imper- 

 vious 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, and 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 con- 

 tact 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, offers 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 appa- 

 rent fatigue, to warble so long and so musically. 



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

 organs, are the seat of the continual vibratory motions pro- 

 duced by cilia, discovered by Professor Purkinje and Dr. 

 Valentin of Breslaw, to exist as a general phenomenon over 

 the internal surface of those parts, and those parts only in 



312 



