646 CIRCULATION:. 



heart (//, H) receives the whole venous blood the body is divided between the portal veins of 



of the body by the right auricle, and a small the liver, and the venae advehentes of the kidney; 



quantity of arterial blood from the lungs by in others a part is also sent into the abdominal 



the left. These two kinds of blood, mixed vena cava. The inferior renal or advehent 



together in the common ventricle, proceed veins of the kidneys (Jigs. 316, 317, and 318, 



from thence into the aortic bulb and its #) carry venous blood to these organs, and 



branches (A, B, b). In the larva of the Sala- distribute it minutely through their substance, 



mander and Protean Reptiles, a part of the It is removed from thence and returned into 



blood is sent by pulmonary vessels to the the great circulation by the revehent or superior 



lungs, from which it is returned by the pul- renal veins (/c) which lead into the vena cava.* 



monary veins to the heart; a part passes di- The anterior abdominal vein (ftp. 316, u) is the 



rectly round the arches, and gains the descend- same to which Bojanus has given the name of 



ing aorta; the greatest quantity passes out into umbilical in the Tortoise, in which class of ani- 



the gills, and after being arterialized returns to rnals it is of very large dimensions, and receives 



be mixed with that in the aorta, so that a not only the venous blood from the posterior 



mixed blood must permeate all the vessels of extremities and shell, but also some from the 



the systemic circulation. In the Siren, accord- anterior extremities. The persistence of those 



ing to Cuvier and Owen, the whole blood goes umbilical veins which proceed from the large 



at once to the gills, from the want of any com- urinary bladder in many of the adult reptiles is 



municating twigs across the root of these a fact of some interest, because it points out a 



organs. It is interesting to remark that the resemblance between the permanent distribu- 



arteries of the head and upper extremities (a) tion of the vessels in these reptiles and the 



are not given off by the aortic arches until fetal condition which we find in the higher 



after they are joined by the returning branchial animals, and likens the bladder of the scaly 



vessels, a disposition which is in some respect Reptiles, as well as of the Batrachia in which 



similar to what we find in higher Reptiles, and during fcetal life no allantoid membrane is ever 



which seems to have for its object the supply formed, rather to an allantoid receptacle than 



of a more pure arterial blood to the cerebral to a proper urinary bladder, 

 organ. Fishes. In fishes there is no vestige of a 



In the larva of the Frog, the course of the pulmonary organ, and the respiration is wholly 



blood is very similar to that of Fishes. The effected by means of the gills. The branchial 



whole of the venous blood propelled through apparatus of fishes is internal or covered, like 



the heart is sent into the gills, and is made to that of the larva of the frog ; it is placed on 



pass through them before reaching any other the cervical part of the alimentary canal, and 



part. From the posterior parts of the first is formed by the fine subdivisions of aortic 



arches are given off the vessels of the head, the arches (Jig. 319, A, B, b*), which are prolonged 



second form the right and left roots of the de- into the fringed or leafy processes of the hyoid 



scending aorta, and the fourth are continued branchial arches. The respiratory organ is 



upon the lungs in the form of a pulmonary thus placed in this class in the course of the 



artery. There is however also in the larva of arterial circulation. The venous blood from 



the Frog a short anastomosis between the out- the body generally, and from the liver, enters 



going and returning artery of each of the gills, the single auricle (A) through the great sinus 



which allows of a direct passage of some blood (V}, and is wholly propelled into the arterial 



round the arches of the aorta. bulb by (A) the single ventricular cavity ( H). 



In the Protean Reptiles and larva of the No systemic arteries come from the aortic bulb, 



Batrachia a greater quantity of blood is sent to but this vessel carries by the arches into which 



the respiratory organ than occurs in the adult it divides (B), the whole of the venous blood 



Frog or Salamander. into the gills. The number of these arches 



Portal circulation in Reptiles. In the class subdividing and ramifying in the gills varies 



of Reptiles there are two lesser venous circula- in different fishes. In a few, as the Lophius, 



dons besides those already described; the one, there are only three on each side. Inmost 



similar to the portal circulation of warm-blooded osseous fishes there are four. In the Skates 



animals, belongs to the liver ; the other, which and Sharks there are five. In the Lampreys 



does not appear to occur either in Birds or there is the greatest number known, namely, 



Mammalia, belongs to the kidneys. According six or seven. 



to Jacobson, who was the first to point out the The blood, after having undergone arteria- 



existence of veins carrying blood to the kidneys lization in the gills, is not returned to the heart, 



in the Amphibia, and the later researches of but proceeds directly through the branches of 



Nicolai and others, there are two principal ves- the aorta <^/zg.319*, b b, A) to different organs, 



sels which carry back blood from the posterior The force of the heart acts therefore through the 



parts of the body, viz. the anterior abdominal, whole of the capillary system of the gills (be), 



and the inferior renal veins. These two vessels and continues to propel the arterialized blood 

 are formed by the union of the iliac, caudal, 



posterior cutaneous, pelvic, visceral, abdominal, * It must be remarked that Meckel, who appears 



and umbilical veins; and in most Reptiles, ex- to have examined the distribution of the above men- 



cepting the Ophidia, the renal and portal vessels tioned vessels with great care, denies entirely the 



proceeding from the posterior parts of the body jj^ el j Jction of the lower veins of the kidneys 



i r> /i *u u i f bot " m fi shes and reptiles, considering all the veins 



arise together. In some Reptiles the whole of of the kidney as rev !; hcnt '. Vergleich. Anat. B.V. 



the blood returning from the posterior parts of 5. 201 and 253. 



