and left; the left is less than the right; that quantity which is wanting to the left lobe is equal to the quantity of a spleen; and if in idea we add the spleen to the left lobe of the liver, both lobes of this organ become quantitatively equal, and the whole liver symmetrical; hence, as the liver plus the spleen represents the whole structural quantity, so the liver minus the spleen signifies that the two organs now dissevered still relate to each other as parts of the same whole. 5thly. The liver, as being three-fourths of the whole, possesses the duct which emanates at the centre of all glandular bodies. The spleen, as being one-fourth of the whole, is devoid of the duct. The liver having the duct, is functional as a gland, while the spleen having no duct, cannot serve any such function. If, in thus indicating the function which the spleen does not possess, there appears no proof positive of the function which it does, perhaps the truth is, that as being the ductless portion of the whole original hepatic quantity, it exists as a thing degenerate and functionless, for it seems that the animal economy suffers no loss of function when deprived of it. 6thly. In early foetal life, the left lobe of the liver touches the spleen on the left side; but in the process of abdominal development, the two organs become separated from each other right and left. 7thly. In animals devoid of the spleen, the liver appears of a symmetrical shape, both its lobes being equal; for that quantity which in other animals has become splenic, is in the former still hepatic. 8thly. In cases of transposition of both organs, it is the right lobe of the liver--that nearest the spleen, now on the right side--which is the smaller of the two lobes, proving that whichever lobe be in this condition, the spleen, as being opposite to it, represents the minus hepatic quantity. From these, among other facts, I infer that the spleen is the representative of the liver on the left side, and that as such, its signification being manifest, there exists no exception to the law of animal symmetry. "Tam miram uniformitatem in planetarum systemate, necessario fatendum est intelligentia et concilio fuisse effectam. Idemque dici possit de uniformitate illa quae est in corporibus animalium. Habent videlicet animalia pleraque omnia, bina latera, dextrum et sinistrum, forma consimili: et in lateribus illis, a posteriore quidem corporis sui parte, pedes binos; ab anteriori autem parte, binos armos, vel pedes, vel alas, humeris affixos: interque humeros collum, in spinam excurrens, cui affixum est caput; in eoque capite binas aures, binos oculos, nasum, os et linguam; similiter posita omnia, in omnibus fere animalibus." --Newton, Optices, sive de reflex, &c. p. 411.]