The author states some observations which he has made on the coloured marks apparent in a variety of the horse, common in Scot- land, and there called the Eel-hack Dun, and which afford grounds for doubting the accuracy of the conclusions deduced in a paper, by the late Earl of Morton, published in the Philosophical Transactions for 1820. The title of the paper referred to is " A Communication of a singular fact in Natural History," namely, that a young chestnut mare of seven- eighths Arabian blood, after producing a female hybrid by a male quagga, had subsequently produced, by a fine black Ara- bian horse, a filly and a colt, both of which had the character of the Arabian breed as decidedly as could be expected where fifteen- sixteenths of the blood are Arabian, but in colour, in the hair of their manes, and the markings of the back and legs, bore a striking resemblance to the quagga.
The author, finding that similar markings are very commonly met with on the Eel-back dun ponies of Scotland, suggests, that as the breed of the mare in question was not pure she may have inherited the tendency to those peculiar markings. He moreover observes, that the cross bar markings on the legs are not found in the quagga, but only in the zehra, which is a species quite distinct from the quagga ; a fact which he considers as completely overturning the reasoning by which the conclusions stated in Lord Morton's paper were deduced. The facts, he thinks, admit of a more natural ex- planation, and one more consistent with the known physiological laws of developement, by supposing the stain in the purity of the mare's Arab blood to have arisen from the circumstance of an early progenitor of the mare having belonged to the Eel-backed dun va- riety, the peculiarities of which reappeared in a later generation.
8. " On the Structure and Functions of the Spleen." By Thomas Gordon Hake, M.D. Communicated by Francis Kieman, Esq., F.R.S.
The author, passing in review the various opinions which have been advanced by anatomists respecting the intimate structure of the spleen, arrives at the conclusion that hitherto only vague and premature inductions have been made. It is generally admitted that the fibrous envelope of this organ is formed of the external fibres of the splenic vein ; and that from the internal surface of this envelope fibrous prolongations are continued into the interior of its substance, giving support to a fine cellular membrane, which is continuous with their edges, and variously reflected so as to constitute cells. The parenchyma, or solid structure of the spleen, everywhere accom- panies these membranous productions, and forms the exterior walls of the cells ; being composed of branches of the splenic arteries, of the granular terminations of those arteries constituting the splenic grains of Malpighi, of venules, which ramify around the splenic grains, and of cellules, into which the venules open, and from which the splenic veins take their rise. The author concludes, as the re- sult of his inquiries, that a dilatable cellular tissue exists, containing venous blood, between the granules within which the arteries ter-
