EDITOR S INTRODUCTION. 3 



The mechanism whereby expiration is effected is equally simple ; just as, when the upper board 

 of the bellows is depressed, the air is forced out through the nozzle, so, by the return of the breast-bone 

 to its former position, the inspired air is again forced to pass through the lungs and make its escape by 

 means of the windpipe. By this process it is obvious that the vital element — the oxygen of the 

 atmosphere — being admitted to every part of the system, the blood is vitalised to the greatest possible 

 extent, its temperature is raised until the heat of the body of a bird is far greater than that of an 

 ordinary quadruped, and its vitality is proportionately exalted. Consequently, as the blood circulates 

 through the system, it carries with it heat and life in superabundance ; the energies of the entire system 

 are roused to the uttermost ; the fibres of every muscle quiver with intense life, like a steam-engine 

 working under high pressure, thus enabling the falcon to cleave the skies with the velocity of a falling 

 thunderbolt, and not only qualifying the swallow for its rapid flight, but enabling it to achieve its 

 wonderful migrations. 



This admission of air into every part of the system serves not only to fan the vital flame, and 

 rouse the energies of the bird to an extraordinary degree of tension ; it likewise assists in giving 

 buoyancy to its movements, bearing it upward, as the gas does a balloon ; for it is evident that the 

 air received into the body being raised to a temperature corresponding to the heat of its blood, the 

 specific gravity of the bird is proportionately diminished, and it rises into the air almost without an 

 effort, and even hovers in the sky with scarcely a perceptible movement of its wings. 



A knowledge of the mechanism of their mode of respiration will likewise enable us to explain 

 another remarkable feature in the history of the feathered tribes, namely, their power of song. Who 

 that has listened to the prolonged warblings of a linnet, the flood of melody poured forth from the 

 little throat of the canary, the " lengthened sweetness long drawn out " which almost pains the 

 enraptured ear as we listen to the song of the nightingale, but has wondered how such tiny birds can 

 ever find sufficient breath for the utterance of such long-sustained, such interminable notes ? 'What 

 would our prima-donnas at the opera give for but the tithe of the capacity of these favoured little 

 songsters ? No human breast could ever hold sufficient breath for such performances. We now see, 

 however, that the vocal organs of a bird are exactly adapted to the nature of their music. Their 

 whole body is a bellows, as large in proportion to their size as the bellows of an organ is in relation 

 to the pipes into which it has to pour the sound. The little bird is, in fact, a living harmonium — its 

 singing apparatus is not situated at the top of its throat, bat is implanted in the inferior termination 

 of its windpipe ; and just as the tongue of the harmonium is thrown into vibration by the issuing 

 current of air caused by pressure upon the bellows, so are the vocal chords of the feathered songster 

 rendered sonorous as the air passes over them. In proportion to the capacity of the bellows must be 

 the duration of the note, and we have already seen that the air-cells of the bird are capable of 

 furnishing a supply not easily exhausted. There is, however, this remarkable difference between the 

 two instruments : the tongue of each key of the harmonium can give utterance but to one sound 

 — one never-varying tone — while the corresponding part of the bird, rendered more or less tense by 

 muscles provided for the purpose, contains within itself a whole gamut, and tiiere is not a note in the 

 scale that is not instantly at the command of the inimitable little musician. In the perching birds, 

 among which are found by far the most accomplished singers, five pairs of muscles are connected 

 with this exquisitely-contrived apparatus, and are so disposed as to influence both the diameter and 

 the length of the air-passages. In the parrots three pairs are met with ; some of the swimming birds 

 have two, while others have only one ; and in a few — as die king of the vultures and die condor — 

 vocal muscles are quite wanting. 



Seeing that the temperature of birds is raised so much above the usual standard by the arrangements 

 described above, some clothing is requisite, adequate to retain the vital heat. Another indispensable 



