96 AMPHIBIA. 



bony plates on each side, probably rudiments these little, pulsating sacs are found ; at the pos- 

 of me vomer and palatine bones. Each of terior part one is situated on each side of the 

 the larger has six or seven lines of teeth, about extremity of the coccygeal bone, behind the hip- 

 twelve on each line ; and each smaller bone joint, and the anterior ones under the posterior 

 bears four ranges of five or six teeth ; making edge of the scapula by the transverse process 

 in all nearly two hundred teeth in the palate, of the third vertebra. These cavities are of 

 Those of the lower jaw in this animal are considerable size, and pulsate with some degree 

 placed in similar order. In the proteus the of regularity : the pulsations, however, do not 

 teeth nearly resemble those of the salamander. coincide with those of the heart, nor are those 



The maxillary teeth are always slender, on the one side always synchronous with 



sharp-pointed, and closely set. The frog has those on the other. The posterior ones convey 



about forty on each side of the upper jaw, of the lymph received from the legs and hinder 



which eight belong to the intermaxillary bone, parts of the body into the ischiatic veins, and 



The salamander has about sixty above and below, the anterior pair, into which the absorbents 



In the tadpole state of the frog the mouth of the arms and the anterior parts of the 



is very small, and, instead of teeth, is occu- viscera, &c. open, convey this fluid into the 



pied only by minute horny plates of just jugular veins. The internal structure of these 



sufficient consistence to abrade the soft mixed sacs is cellular ; they communicate freely 



food which it finds on the surface of animal with each other on each side by anastomosing 



or vegetable substances in the water. Its sto- vessels. On inflating the organ, not only the 



mach and intestinal canal are of very different lymphatic vessels are inflated, but the whole 



form from that which they afterwards assume, of the veins also. Dr. Marshall Hall had 



The intestine is of nearly equal size throughout previously observed a somewhat similar pul- 



its whole length. It is very long, being not sating cavity in the eel. 



less than ten times the length of the actual These lymphatic ventricles in the amphibia 



space from the mouth to the anus, and is coiled have still more recently received further exami- 



up in a circular form, occupying the greater nation and illustration by Professor Panizza 



part of the abdominal cavity. The canal, as of Pavia, who published the result of his 



we shall presently see, changes its character researches in the year 1833.* Professor Muller's 



materially during the metamorphosis of the discovery was published in the previous year 



animal, becoming gradually shorter until it is in the Berlin Annals. 



not a quarter of the length, in proportion to The lymphatic system is developed to an 



the size of the animal, which it exhibited in extraordinary degree in the frogs, as well as 



its earlier condition. in several other genera of this class, its vessels 



In the adult amphibia the whole alimentary being found ,in numbers and of considerable 



canal is of a very simple character. The size immediately under the skin, 



esophagus is wide and comparatively short. The lacteals ramify upon the surface of the 



The stomach single, consisting of a simple sac, intestine in two layers, anastomosing and 



elongated in the lengthened forms of the sala- forming intricate plexuses on the mesentery, 



mander, the proteus, and other aquatic species, and terminating in two trunks, or thoracic 



The intestine is but slightly convoluted, even ducts, which pass forwards one on each side 



in the short tailless family ; and there is com- of the spinal column. 



paratively little difference in the diameter of V. Of' the sanguiferous system. If the 



its two distinct portions. It terminates, as in changes, so frequently alluded to, which the 



the reptilia, in a cloaca, or pouch, which also animals of this class undergo in passing from 



receives the openings of the urinary and genital the condition of a fish to that of a reptile, have 



organs. The anus in the toads and frogs opens received repeated illustrations in the considera- 



on the hinder part of the back ; in the other tion of the structure of the skeleton, of the 



forms it is situated beneath at the commence- organs of motion, and of those of digestion, far 



ment of the tail, as in the reptilia. more interesting and important are those which 



The liver, the pancreas, and the spleen are occur in the character of the circulation ; in 

 found in the whole of the amphibia ; and which the view which has been taken of the 

 these organs are observed, in the elongated true situation of the amphibia in the chain of 

 aquatic forms, to assume a corresponding animal development receives the most satis- 

 lengthened shape. The liver is of considerable factory proof. Beginning life with all the 

 size, particularly in the salamanders. The essential characters of the fishes, even in the 

 gall-bladder exists in all cases, varying, how- functions of circulation and respiration, pos- 

 ever, in size and form in the different genera. sessing the single branchial heart of that class, 



IV. Lymphatic and lacteal system. This how wonderful and beautiful are the changes 



system is highly interesting in the amphibia, which these systems of organs undergo, as the 



on account of its extreme development, and branchiae become obliterated to give place to 



of its presenting several important and remark- pulmonic cavities, and the heart at the same 



able peculiarities in its structure. time assumes the compound character and form 



The investigations of Professor Muller of of a systemic and pulmonic heart, in accordance 



Berlin have lately brought to light the existence with the change in the respiratory organs, 



of pulsating cavities in the course of the lympha- The newts, or water-salamanders, afford the 



tics, constituting a sort of ventricles for the pro- most satisfactory opportunity of observing these 



pulsion of their fluids towards the veins into * Sopra il sistema linfatico dei rettili. fol. Pav. 



which they are received. In the frog two pairs of 1833. 



