164 



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 "v\4th 

 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- 



