352 FISHES. 



show the numerous membranous lamina of which it is composed, 

 and which are lined at each of their surfaces with a number of eggs 

 so considerable, that when they have acquired their natural develope- 

 ment, they entirely hide the membrane to which they adhere. 



CHAPTER VII. 



Organs of Nutrition of Fishes * 



The vegetative functions of fishes foUoAv the same order as those of 

 the other vertebrated animals ; they seize and divide their aliment 

 with the teeth ; they make it undergo a first digestion in the stomach ; 

 passing from that organ into the intestinal canal, the food receives 

 the bile which is poured out by the liver, and in some fishes there is an 

 addition of a liquor which is analogous to the pancreatic secretion ; 

 the nutritive juices which are absorbed by means of vessels which 

 represent our lacteals, and perhaps are partly taken up by the veins, 

 are blended with venous blood ; this is carried to the heart, and from 

 the heart to the gills where the contact of the surrounding air con- 

 verts it into arterial blood ; the latter then returns to nourish the whole 

 of the body ; but the blood must also be carried out of the body in 

 various ways, and this is effected by perspiration, by the various 

 liquids that ooze from the skin and the kidneys, which produce 

 urine. 



We shall in this chapter describe the organs of manducation, of 

 digestion, of circulation, of respiration, and then the excretions. 



Fishes in general are characterised by voracity ; we see them in- 

 cessantly pursuing and devouring each other, or bolting small animals 

 found within their reach; their ability, however, in this respect, will 

 depend, it is obvious, on the opening of their mouth and the power 

 of their teeth ; if the teeth be sharp and crookened, they are then 

 able to retain the most agile animals; if the teeth are large and 

 strong, then can they grind down the hardest prey ; but when the fisli 

 is furnished only with weak teeth, or vitterly destitute of them, he is 

 reduced to live on food which cannot offer the least resistance. 



* The splanchnology and angeiology of tlie perch are represented in plates vii. and 

 viii. Figure 1, pi. viii. represents a perch opened, showing the heart and abdominal 

 organs, with the omenta in their natural situation. Figure ii, pi. viii. shows the 

 same organs and the gills in their jn-oper situation, and are seen on the left side, 

 after raising the opercula, the bones of the shoulder, the muscles, and the peritonaeum 

 of that side : this figure was taken from a female whose overy was quite full. The 

 large figure of plate vii. represents a perch in which all the muscles and the perito- 

 naeum of one side are removed, and in which the opercular pieces and the other 

 lateral apparatuses of the head and shoulder are detached and turned down ; this 

 shows ths branchia quite naked, also the heart and the sinuses of the veins, with 

 arteries which pass from the gills, the arteries, and veins of the trunk, and all the 

 abdominal viscera, with their arteries and veins ; a great portion of the cerebral 

 nerves, and the first nerves of the spine are shown also, according to their distribu- 

 tion ; the rest of those of the spine has been witheld, least the figure would be con- 

 fused by a complication. This figure was taken from a female in which the overy 

 ■was very slightly developed. Figure iii. pi. viii. gives the intestinal canal and the 

 liver, which are separated in such a way, as to display the distribution of the vena 

 portw and the gall bladder. 



