Their peculiar vessels and nerves I have never witnessed.
3. The trabecular tissue, (trabeculo lienis, balks, or joists of the spleen), consists of white, shining, flat or cylindrical fibres, which arise in great numbers from the inner surface of the fibrous coat; and, in smaller quantity-, from the exterior surface of the sheaths of the ves sels. These are so connected with similar fibres in the interior of the spleen as to con stitute a network which extends throughout the whole organ. Between the fibres of this net exist a great number of spaces which are connected with each other, and are occupied by the red spleen-substance and splenic cor puscles ; and which, although very irregular in respect of their form, and, as regards their size, of the most variable dimensions, have yet a considerable resemblance to each other. The older anatomists regarded these spaces as regular and uniform cavities provided with a special membrane. But this last structure nowhere exists, as may be verified in a spleen in which, after short maceration, the pulp has been removed from these spaces by washing. Such a preparation will also affbrd the best means of studying the mode of connection of the fibres, and in this manner it may be seen that, although they are of very different diame ters, yet the finer fibres are not everywhere given off from the thicker ones. This is es pecially shown by the fact, that fibres of the most different diameters are intimately con nected together at all points. Where four, five, or more of these joists meet, there generally oc curs a knot of a flattened cylindrical form, which is not unlike that of a nerve-ganglion. Such knots are more frequently found to wards the outer surface of the organ, since the cross-beams are more numerous ,here than in the interior. In this latter part, namely in the neighbourhood of the great vessels, the nume rous ramifications of these tubes themselves serve as points of support to the pulp, and consequently render the joists less necessary.
The structure of the trabecular tissue of the human spleen completely corresponds with that of the fibrous tunic, since it consists of white fibrous tissue and the yellow fibres. The former of these two structures exhibits parallel fibrilhe, which run without exception in the direction of the long axis of the parti tion or joist, and rarely unite into individual bundles. The latter consists of somewhat finer and stronger yellow fibres, which anas tomose with each other ; their maximum di ameter is 1,1000th of a line : the greater number of them lie between the bundles of white fibrous tissue, and are easily recognised by their irregular course and manifold curves.
Many anatomists, with Malpighi, had spoken of muscular fibres in the partitions of the spleen, although none had succeeded in de monstrating them, either with the scalpel or microscope, or chemically. But in 1846 I dis, covered them with the aid of the microscope, in the spleen of the pig.* IIere they exist both in the finest and largest of the partitions, but they are not isolated, being connected with the finer reticulations of the yellow fibres (fig. 523.). In the larger partitions which are visible to the naked eye, the muscular and elastic fibres are present in pretty nearly equal quantities, consequently these parts are to be regarded as alike elastic and contractile. But in the smallest and microscopic cross-beams the muscular fibres predominate, and often they appear to be even unmixed with elastic fibres. In these parts the quantity of white fibrous tissue is still smaller than that of the yellow ; indeed, in this animal it is but very sparingly present in the larger partitions. The direction of the fibres above-named is always longitudinal or parallel to the long axis of the joist, never transverse,. In similar extent and quantity, and with a like connection to the elastic tissue, I have found muscular fibre in the dog, the ass, the cat, the Dicotyles tor quatus, the sheep, rabbit, horse, hedgehog, guineapig, and bat. In the ox, on the con trary, it exists only in the finer and micro. scope partitions, where it is present in very considerable quantity and in remarkable dis, tinctness. The remainder of the trabecular tissue consists only of yellow fibre in uhion with some white fibrous tissue. As to the lower vertebrata, I have examined a great number of them with respect to this muscular structure, and have found that the smallness of the spleen in many of them offers a great obstacle to observation ; yet I believe I have verified that the spleens of the pigeon, sparrow, blindworrn, tench (tinca chrysitis), and trout, contain muscular fibres. So, also, my friend Professor Ecker, of Basle, has orally commu nicated to me that he has found very dis tinct muscular fibre in the spleens of the ray and shark.