File:A history of birds (1910) (14563068498).jpg

Identifier: historyofbirds00pycr (find matches)
Title: A history of birds
Year: 1910 (1910s)
Authors: Pycraft, W. P. (William Plane), 1868-1942
Subjects: Birds
Publisher: London, Methuen and Co
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: Biodiversity Heritage Library

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the Owls, it is true, still partake freely of insect food,but so also do many of the smaller Falcons, which indeed liveexclusively on this diet, yet they, like their larger brethren, areminus these organs. One must assume that they were lostbefore the insect diet became fixed, and so could not be re-developed. But it is clear that they are not essential to thedigestion of insect food, and equally clear that the substitutionof a carnivorous diet need not bring about their dissolution. The rectum, like that of reptiles, terminates in a cloaca di-vided into a series of more or less distinct chambers, the copro-daeum, urodi^eum and proctodaium, into which last opens the Bursa Fabricii, an organ of unknown function, peculiar tobirds, and largest in nestlings ; into the uroda^um open thekidney and the genital-ducts. The coproda^um retains thefaecal and urinary matter until ready for expulsion. The Circulatory System The main features of the circulatory system may be verybriefly summarised.
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III. 7.—Types OF the C/eca, or Blind Gut, of I. Rhea. II. Owl.III. Martineta Tinamou INTRODUCTORY 25 Birds differ from Reptiles and agree with the Mammalia inhaving a completely four-chambered heart, whereby the ad-mixture of arterial and venous blood is prevented. The heartof birds, however, differs in important respects from that ofmammals. Owing to their excessive activity the heart-beats of the birdare quicker than in any other animals, numbering 120 to theminute during rest, and during flight reaching a far higherfigure. In a bird which has just alighted the pulsations arebeyond the count of the ear. Birds, like mammals, have but a single aortic arch, but whilein the former this is the left, in the latter it is the right of theoriginally double arch which persists. The corresponding archof the opposite side, in both cases, gives rise to part of thesubclavian artery. The carotid arteries exhibit some interest-ing modifications, but these appear, like so many other char-acters, t

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