CLASSIFICATIONS OF THE AMPHIBIA. 371 



ological Catalogue of the Hunterian Collection' (vol. ii. note, 

 p. 151), calling the imperfect branchial organs gills, thus de- 

 scribes them. — " The gills are composed of three cartilages, 

 which are placed in the same manner as gills in fish ; but 

 these cartilages have neither the pectinated part nor the mush- 

 room partition, which those of fish have ; their ends are arti- 

 culated together, and the whole is joined to the extremity of 

 the same bone as that of the tongue. From the fauces there 

 is an opening outwards, between the two inferior cartilages of 

 the gills, for the water to pass. In this opening, which is 

 oblong, is placed a structure composed of two valves, which 

 will obstruct the water passing in from without. The two 

 cartilages which are above the opening, between which the 

 two arteries pass, are lined on the inside by the membrane of 

 the fauces, which is not very thin." Next, the aorta, or great 

 artery, arising from the ventricle of the heart, swells at its 

 upper part into a bulb-like bag (bulbus arteriosus), from the 

 extremity of which there proceed eight smaller arteries, four 

 diverging to the right side and four to the left; one of the 

 lower arteries, on each side, passes downwards and enters up- 

 on the top of each lung, along which it ramifies, and forms 

 the pulmonary artery. x The other arteries branching off from 

 the arterial bulb on each side, proceed outwards to the gills, 

 and becoming the branchial arteries, " there wind round and 

 between the cartilages of those parts, 1 ' both on the left and on 

 the right side ; thence, coming round towards the back, they 

 unite into a single trunk on either side, which, running to the 

 backbone, afterwards constitute (with other branches) the aor- 

 ta descendens. This organization then proves the circulation 

 of the blood to be twofold, and in fact branchipulmonary, or 

 pneumobranchial, as it has been well named by Hunter, for 

 there are two distinct arteries (pulmonary) leading to the two 

 lungs, and as many separate branchial arteries wind around 

 the gill-like organs, as there are such organs or gills in num- 

 ber. 2 This circulation is nearly identical with that of the 

 animals in the next order of Amphibia, which have complete 

 and persistent branchice ; the only difference is, that in the 

 latter the branchial arteries send off branches, which enter and 

 ramify through the external gill-tufts attached to the ends of 

 the hyoidean arcs, in order that the blood may be more sub- 

 jected to the influence of the water. Now, I cannot imagine 



1 But the pulmonary artery in the Menopoma springs from the end of one 

 of the branchial arteries. 



2 Cuvier says, — "tant que les hranchies subsistent, l'aorte, en sortant du 

 cceur, se partage en autant de rameaux, de chaque cote, qu'il y a de bran- 

 chies." 'Regne Animal,' tome ii. p. 101. 



