Outlines of Zoology and Comparative Anatomy (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated.1874 Excerpt: ... CHAPTER VI. Amphibia. Amphibia (Batrachia, Cuvier), also termed diplopnaea (SraAfj. double; and irvoij, breathing), are knowu by the following characters: --They all possess branchiae, which are either deciduous or permanent, hence, they have been divided into the caduci-branchiata and perenni-branchiata; true lungs are always present in the adult. There are always two occipital condyles for articulating with the vertebral column. The vertebral centra vary much, being amphicaelous in the ophiomorpha (&ipis, a snake; and nopi)rf), form), opisthocaelous in the salamanders (aaanavSpa, a lizard), and procaelous in most of the others. When limbs are present, they are never converted into fins, but possess the same skeletal elements as tho9e of the higher vertebrata. Their bones, both in chemical composition and in structure, are very similar to those of fishes; they have no medullary canal, no laminated arrangement, but the plasmatic canals exhibit slight dilatations, The heart, in the adult, consists of two auricles and a single ventricle. The nasal sacs communicate with the pharynx. The skin is smooth, glutinous, and almost always destitute of scales. There are never fin rays present, though median fins sometimes exist. There is a common cloaca. The embryo never possesses an amnion, and the urinary bladder represents the allantois. Lastly, they all undergo a metamorphose after leaving the egg. All amphibia commence their existence as water-breathing larvae, provided with branchiae and possessing all the attributes of fishes; in some, only external branchiae are present, in others both an internal and external set are developed; the external branchiae are the first to disappear, and subsequently, when the lungs are fully developed, the internal. In the perermi-b..