562 SPECIAL HISTOLOGY. 



169. Vessels and nerves. As they enter the organ, the relatively 

 very large splenic artery and the still larger splenic vein, are accompa- 

 nied by those processes of the fibrous membrane, which have been 

 referred to as the vascular sheaths. In Man these processes form com- 

 plete investments around the vessels and nerves, somewhat after the 

 fashion of the capsule of Glisson, so that the arteries and nerves espe- 

 cially, can be readily isolated, while the veins, which on the side opposite 

 to the artery are more intimately connected with the sheath, are less 

 easily separable. At first the sheaths are as thick as the fibrous coat 

 itself and they retain this thickness so long as they surround the prin- 

 cipal branches of the vessels. The finer ramifications of the latter and 

 even those small branches which are given off from the large ones, have 

 finer and finer sheaths, until at last, when the vessels are quite minute, 

 they become lost as thin membranes in the pulp. The thickness of any 

 sheath is always less than that of the wall of the artery to which it 

 belongs and greater than that of the vein, but after division the sheaths 

 become relatively stronger. It was remarked above, that a number of 

 the trabeculce are inserted into the vascular sheaths and they therefore 

 take a share, together with the vessels w T hich they inclose, in the forma- 

 tion of the dense network in the interior of the spleen. In Mammalia, 

 as in the Horse, Ass, Ox, Pig, Sheep, &c., the sheaths present different 

 relations, inasmuch as the smaller veins have none at all, and the larger 

 possess them only on the side on which the arteries and nerves lie. Only 

 the two principal venous trunks near the Jiilus have perfect sheaths, 



Remak's very valuable and elaborate paper, " Ueber runde Blutgerinnsel und iiber Pigment 

 kugel haltige Zellen," in Muller's " Archiv," for 1852, and Mr. Wliarton Jones's article on 

 the same subject in the "British and Foreign Med. Chir. Review," for 1853, to which we 

 have already referred. Having carefully studied them, he will, we think, arrive very much 

 at our own conclusion, that as the question now stands, the very existence of " blood-cor- 

 puscle-holding cells" must be considered as highly problematical. 



Mr. Wharton Jones found the blood of the splenic vein to contain nucleated corpuscles 

 and fibres identical with those of the pulp, together with free nuclei similar to those of the 

 nucleated corpuscles; on the occurrence of which, he considers the statements as to the 

 abundance of colorless corpuscles in the blood of the splenic vein are founded. Some of 

 these elements were traced as far as the vena portee, but in the hepatic veins they had mostly, 

 though not entirely, disappeared. He appears to be inclined to draw the conclusion that 

 some of the venous radicles of the spleen are connected with the pulp in the same way as 

 the hepatic ducts with the parenchyma of the liver, and that the materials thus derived by 

 the blood from the spleen may concur in fitting it for the secretion of bile. Moleschott 

 ('Ueber die Entwickelung cler Blutko'rperchen," Muller's "Archiv," 1853), gives some 

 curious results obtained by extirpating the liver and spleen of Frogs. Normally, the car- 

 diac blood of Frogs contains about 8 red corpuscles to 1 colorless ; after extirpation of the 

 liver, the proportion is 2-3 red corpuscles to 1 colorless. The blood of the spleen of Frogs 

 contains, normally, six times fewer red corpuscles in proportion to 1 white, than that of the 

 heart. After extirpation of the liver, there are 1-G colorless corpuscles to 1 red corpuscle 

 in the splenic blood. When the spleen alone has been extirpated, the proportion of red 

 corpuscles is slightly increased. Moleschott concludes that the liver favors the metamorphosis 

 of colorless into red corpuscles. However, we must confess that the results of the individual 

 experiments, from the average of which his conclusions are drawn, vary so widely as to 

 throw some doubt on the latter. TRS.] 



