24 



VERTEBRATE AXDIAXS. 



Div. 1. 



The blood is always red, and appears to have a composition proper for sustaining that 

 energy of sentiment and vigour of muscles, but in different degrees, which correspond 

 to the amount of respiration, from which originates the subdivision of the vertebrate 

 animals into four classes. 



The external senses are alwaj's five in number, and reside in two eyes, two ears, two 

 nostrils, the teguments of the tongue, and those of the body generally. Certain species, 

 however, have the eyes obliterated. 



The nerves reach the medulla through perforations of the vertebrpe, or of the cra- 

 nium : they all seem to unite with this medulla, which, after crossing its filaments, 

 expands to form the various lobes of which the brain is composed, and terminates in 

 the two medullar}' arches (vuutes) termed hemispheres, the volume of which con'e- 

 sponds to the amount of intelligence. 



There are always two jaws, the principal motion of which is in the lower one, 

 which rises and falls ; the upper is oftentimes entirely fixed : both of them are almost 

 always armed with teeth, excrescences of a peculiar nature, the chemical composition of 

 which is very similar to that of bone, but which grows by layers and transudations ; 

 one entire class, however, (that of birds,) has the jaws invested with horn*, and the 

 group of tortoises, in the class of reptiles, is in the same predicament. 



The intestinal canal is continued from the mouth to the anus, undergoing various 

 inflexions, and several enlargements and contractions ; having also appendages, and 

 receiving solvent fluids, one of which, the saliva, is discharged into the mouth : the 

 others, which flow into the intestine only, have various names ; the two principal are 

 the juices of the gland called the pancreas [or siceet-hrecul], and the bile [or gciIQ, 

 which is the product of another very large gland, named the liver. 



While the digested aUment is traversing its canal, that portion of it which is proper 

 for nutrition, and is termed the chyle, is absorbed by particular vessels, named lacteals, 

 and carried into the veins ; the residue of the nutriment of the parts is also carried into 

 the veins by vessels analogous to the lacteals, and forming with them one same system, 

 designated the lymphatic st/stem.f 



The veins return to the heart the blood which has served to nourish the parts, to- 

 gether with the chyle and lymi)h with which it has been renewed ; but this blood is 

 obliged to pass, either wholly or in part, into the organ of respiration, to regain its 

 arterial nature, previous to being again dispersed over the system by the arteries. In 

 the three first classes, this organ of respiration consists of lungs, that is, an assemblage 

 of cells into which air penetrates. In fishes only, and in some reptUes while young, it 

 consists of gills, or a series of laminre between which water passes. 



In all the vertebrate animals, the blood which fui-nishes the liver with the materials 

 of the bile is venous blood, which has circulated partly in the parietes of the intestines, 

 and partly in u peculiar body named the spleen, and which, after being united in a 

 trunk called the vena porta, is again subdivided at the Uver. 



• M. r.cortr...T St. Ililairr hu dcicribcd n itructurc in the bill of 

 blnl. wliiih prciciiti ionic •(.(.romh to a tlciit^irT ly&tcni. In a fartus of 

 > rvT.><]ttCt iic»tlr remdr for liatchini;, he fouiiil thit the marciiis of the 

 bill were b«»cl » lib tubcrclci «rraii|{cd in a rcBuUr order, and havihR 

 all the citerior appearance of leetb ; Ihrie tubereiei were not, indeed 

 Imiilanled in the Jawbone!, but formed part of the cMerior sheslh of 

 Ibe bill, f nder each labcrclc. however, there »a« a gelatinous pulp, 

 analopiai to the pnlpi »hlch .ceretc teeth, but resting on the eilRC of 

 the maiillaiTT bonei, and every pulp was lupplicd by veiaels and nerves 

 trareninic a ean il in the sub.l.->nee of the bouc. These lubcrclei form 

 the trsi margini of the loaudiblcs, and their rcniaiui arc iudicatcd by 



canrils in the horny sheath, subsequently formed, which contain a 

 softer material, anil which commence from small foramin.i in the mar- 

 gin of the bone. In certain other birds (as the Mergansers) also, the 

 lateral edges of the bill are provided with horny processes or lnmin:c 

 secreted by distinct pulps, and analogous in this respect to the «b;i!e- 

 bonc Inrnin.T of the Whales, which arc toothless Mammatta, :is arc also 

 the ant eaters ^u<i MouQtrciHiita : it is further remarkable that the. 

 rudiments of dcntitiuu occur iu the fatiu of the toothless Whales. 

 — Ku. 



t Tlic lymphatic TesseU are aluo the media of cutaneous transada- 

 tiou.— Ko, 



