STRUCTURAL DISTINCTIONS. 9 
‘The pulmonic auricle,” continues the learned Professor, “thus 
augments in size with the more exclusive share taken by the lungs 
in respiration; but the auricular part of the heart shows hardly 
any outward sign of its diversion in the Batrachians. It is small 
and smooth, and situated on the left, and in advance of the ventricle 
in newts and salamanders. In frogs and toads the auricle is ap- 
plied to the base of the ventricle, and to the back and side of the 
aorta and its bulb.” 
In the lower members of the order the single artery from the 
ventricle sends, as in fishes, the whole of the blood primarily to the 
branchial organs, and in all Batrachians at the earlier aquatic 
periods of existence. In the Newt, three pairs of external gills are 
developed at first as simple filaments, each with its capillary loop, 
but speedily expanding, lengthening, and branching into lateral 
processes, with corresponding looplets, these blood-channels inter- 
communicating by a capillary network. The gill is covered by 
ciliated scales, ~ which change into non-ciliated cuticle shortly before 
the gills are absorbed. In the Proteus anguinus, three parts only 
of branchial and vascular arches are developed, corresponding with 
the number of external gills. In Szvenx lacertina the gills are in 
three pairs of branchial arches, the first and fourth fixed, the second 
and third free, increasing in size according to their condition. 
Thus, the ‘Amphibia have, at some stage of their existence, both 
gills and lungs co-existent ; respiring by means of branchize or gills 
while in the water, and by lungs on emerging from it. 
All these creatures seem to have been well known to the 
ancients. The monuments of the Egyptians abound in represen- 
tations of Frogs, Toads, Tortoises, and Serpents. Aristotle was 
well acquainted with their form, structure, and habits, even to 
their reproduction. Pliny’s description, however, presents some 
amount of error and exaggeration. Darkness envelops their history 
during the Middle Ages, from which it gradually emerges in the 
early part of the sixteenth century, when Belon and Rondeletius 
in France, Salviani in Italy, and Conrad Gesner in Switzerland, 
devoted themselves to the study of natural history with great 
success. In the latter part of the same century Aldrovandi appeared. 
During fifty years he was engaged in collecting objects and making 
drawings, which were published after his death, in 1640, being 
edited by Professor Ambrossini, of Bologna, the reptiles forming 
two volumes: in these volumes, twenty-two chapters are occupied 
by the Serpents. But the first arrangement which can be called 
systematic was that produced by John Ray, who based his system 
R * 
