Injected and dissected to show the chief features of the circulatory organs, and especially the connected systems of the renal-portal and epigastric veins, together with certain portions of the muscular system, the renal and reproductive organs.

Common Frog, Rana temporaria.

Plate III. Common Frog, Rana temporaria.

THE integument has been turned back on the right side, together with the musculo-cutaneous vein, the superficial branches of which extend from the knee to the shoulder; part of the muscular wall of the body has been removed on that side, but part has been left in situ; and the main trunk of the musculo-cutaneous vein is seen crossing a slip which the obliquus externus muscle receives from the scapula; on the left side the muscular and cutaneous elements of the wall have been turned back whilst remaining in their natural connection with each other and with the epigastric vein; the shoulder girdle has been cut through the middle line, and fastened out on either side so as to expose the lungs, heart, and great vessels; the liver has been removed with the exception of a small part of its substance, as have also the stomach and intestines down to the lower end of the rectum.

a. Intermandibular space. The skin is left in situ anteriorly in the symphysial angle; immediately posteriorly to its cut edge is seen part of the mylohyoid or submaxillaris muscle; and posteriorly again, and at a deeper level, the converging hyoglossi in the middle line, and on either side of them the geniohyoids.

b. Tetradactyle hand. The first finger, i. e. second digit, or 'thumb' socalled, has its basal joint more or less tumid in this, a male specimen.

c. Muscles of thigh. The line points to the sartorius, which is bordered externally by the vastus internus, and internally by the adductores and recti interni. See Ecker, Die Anatomie des Frosches, p. 115.

d. Point where the musculo-cutaneous veins, constituted by factors from the regions of the head and face, but mainly from those of the back and flanks, turn inwards to pass over a slip going from the scapula to the external oblique muscle and join the subclavian vein. As the skin is moist and glandular this vein has probably to a certain extent a respiratory function. See Ecker, l. c., p. 88.

e. Vein, called 'epigastric' by Rathke, 'umbilical' by Bojanus and Jourdain, 'vena portae accessorial and 'vena abdominalis inferior s. anterior', by other authors. This vein is mainly constituted by the convergence of the two transverse branches from the femoral veins seen at f in the figure, but it receives twigs also from the abdominal parietes, and a factor of especial significance in the shape of the vesico-hemorrhoidal vein from the allantoid bladder and rectum.

The occasional pathological distension in liver diseases of the veins of the anterior abdominal parietes in the human subject shows that an arrangement may exist in a rudimentary condition in the higher Vertebrata similar to that shown here to exist functionally between the epigastric and the parietal veins; and the connection with a vesico-hemorrhoidal vein, whilst it may be held to foreshadow the arrangement of the umbilical vein in the foetus of Mammals, puts prominently forward the fact that anastomoses exist between the portal and systemic veins. For the 'renal portal' of the Frog, see Jourdain, A. Sc. N. (4), xii., 1859, p. 180.

f. Point where the transverse branch of the femoral vein of either side fuses with its fellow to form the trunk of the epigastric. g. 'Renal portal,' or renal inferent vein of the right side, being the other branch of the bifurcating femoral vein, which is thus seen to be continuous with the portal systems of both liver and kidney. Consequently there are two channels open for the return of the blood to the heart.

h. Bifid allantoid bladder distended, with ramifications of the vesico-hemorrhoidal veins.

i. The rectum, which is cut short.

j. A vesicular, and in this species glandular, dilatation developed upon the Wolffian duct, by which both testicular and renal products pass down to the cloaca. A vein passes directly into the kidney from it.

k. Vena cava inferior, constituted mainly by the efferent kidney veins, but receiving also those of the testes and fat bodies.

l. Testis of left side. It has, together with its fellow and with the kidneys, been displaced a little to the right side.

m. Fat bodies.

n. Spleen. To the left and a little above the spleen are seen the cut ends of two vessels, one of which receives a factor from that organ, coming itself from the intestine, and the other of which takes origin from the stomach. Both veins join a branch of the epigastric, and are distributed to the liver, a small portion of which is seen left immediately above them.

o. Gall bladder left attached to the epigastric vein by a vein which passes from it to that vessel.

p. Lung of left side. The cavity seen on the outer side of either lung has its outer wall constituted by the internal abdominal muscle (homologous with the internal oblique and transversalis), which arches inwards in a dome shape, and is connected with the oesophagus and pericardium, the coracoid and hyposternum. In the natural condition of the parts these cavities are however mainly occupied by the lobes of the liver, which nearly entirely cover the lungs in an anterior view.

q. Heart The conus arteriosus takes origin from the base of the ventricle, a constriction known as the freturm Halleri marking the line of separation of the two organs. The conus bifurcates into the two great divisions of the truncus aortae, which are each subdivided by internal partitions into three canals. These canals become three tubes, the carotico-lingual, the aortic, and the pulmonary trunks, of which the first is most internal and anterior, and the last the most external and posterior.

q'. Conus arteriosus, with the auricles one on each side. It inclines to the left, and is attached on that side to the ventricle by the frenulum bulbi of Brucke. Denkschrift. Akad. Wien, Bd. iii. 1852, p. 355.

r. Lingual branch of the first of three trunks arising just internally to a rete mirabile known as the 'carotid gland,' from the outer side of which the carotid artery, called sometimes the 'ascending pharyngeal,' passes to the back of the oesophagus in close apposition with the second main trunk or aorta.

s. Convergence of hyoglossi muscles.

t. Geniohyoid muscle.

u. Left external jugular vein passing down to unite with a vein formed by the union of the cutaneous vein with the vena anonyma, and thereby constitute the vena cava superior of the same side.