14 ORGANS OF NUTRITION OV FISHES. 



and backwards like a piston ; so that the animal can make use 

 of this apparatus, either to fix itself upon 

 another body, or to pump up the fluids 

 which may form a part of its nourishment. 

 It is commonly supposed that the Lampreys 

 attach themselves by suction to the bodies 

 of other Fishes, and then eat into their 

 substance, but it seems more probable 



FIG.357.-MQUTHOFTHE fo()d 



animals. 



554. The mouth is not surrounded by any salivary gland. 

 The oesophagus is short; the stomach and the intestines vary in 

 size and form. The liver is generally large, and of a soft tissue ; 

 the pancreas is nearly always replaced by peculiar coecal append- 

 ages placed around the pylorus ; the position of the anus varies 

 much ; sometimes it is found under the throat, at other times 

 under the tail. The kidneys are extremely large, and extend 

 themselves on both sides of the vertebral column, through the 

 whole length of the abdomen. Their excretory passages end in 

 a kind of bladder, whose external opening is placed immediately 

 behind the anus and the orifice of the reproductive organs. The 

 digestive process appears to be performed very rapidly ; and the 

 chyle is absorbed by numerous lymphatic vessels, which empty 

 themselves by several trunks into the venous system near the 

 heart. 



555. The blood of Fishes, as already mentioned, is red; 

 and the globules have an elliptical form, and are of consider- 

 able dimensions. The heart is placed under the throat, in a 

 cavity divided from the abdomen by a kind of diaphragm, and 

 protected by the pharyngeal bones above, by the branchial 

 arches on the sides, and in general by the humeral girdle behind. 

 It is composed of one auricle, which receives the venous blood 

 collected into a large sinus situated in its neighbourhood ; and 

 of a ventricle placed beneath it, and giving rise at its anterior 

 extremity to a branchial artery, which is swollen out at its 

 origin into a bulb. This vessel soon divides into lateral branches, 

 which are distributed to the gills ; and the blood, after having 



