ORGANS OF THE BODY. 



433 



of these pulp elements is composed of a network of fine circular fibres anasto- 

 mosing at acute angles, which constitutes the boundary of the blood stream. 

 These venous passages are clothed with a peculiar species of vascular 

 cells. The latter are, as regards form, fusiform elements (fig. 42 I,/, g, 

 h), and present in man round and projecting nuclei. They lie in the long 

 axis of the venous path, crossing, consequently, at right angles the meshes 

 of the cellular network. They are non-adherent to one another a pecu- 

 liarity of the utmost importance and on this account may easily present 

 clefts between them if the venous passage be subjected to a more than 

 ordinary distending force. Here, then, the distinctly impervious walls of 

 other venous canals do not exist. The vascular cells in question have 

 long been known, from the fact of their extending back into the larger 

 venous trunks, but they were only recognised a few years since in the 

 venous pulp passages by Billroth. They are to be seen with great dis- 

 tinctness in the human spleen. 



In the small meshes of the network of the pulp cords are entangled the 

 same lymphoid cellular elements in pairs or singly, which we have already 

 mentioned when speaking of the follicles and metamorphosed sheaths of 

 the vessels. Pigmentary cells, and even free aggregations of pigment 

 granules, golden yellow, brownish, or black, occur with such frequency in 

 many spleens, that even to the unaided eye the colour of the pulp 

 presents great variety. 



In addition to these elements a certain number of coloured blood 

 corpuscles are regularly met with, at one time unchanged, at another 

 twisted, distorted, and altered. In preparations which have been carefully 

 managed, moreover, the important fact may be 

 noticed with comparative ease, namely, that 

 these corpuscles are situated in the meshes of 

 the tissue of the pulp perfectly free, that is. 

 unenclosed by any capillary walls. 



On leaving the bloodstream they, undergo, 



in fact, changes of various kinds ; they shrink, 



they become fissured, and are thus converted 



into those pigmentary molecules of different 



kinds already alluded to. 



But the most remarkable feature in this 



decay of .the red elements, is the production of 



those cells of the spleen containing coloured 



corpuscles, known now for many years. These 



structures, which were a puzzle to the observers 



of early times, and to which have been given 



consequently the most various signification, have 



been already considered at pp. 77, 78. Here, 



as in other organs, the vital contractility of the 



membraneless bodies of the lymphoid cells 



enables them to take up into their interior, not 



indeed the whole blood corpuscle, perhaps, but 



fragments of its substance. That the lymphoid 



cells of the spleen possess this power of contracting, I saw myself very 



clearly some years ago in water salamanders and frogs. 



Later still the phenomenon was observed most extensively among 



mammals also, by Cohnheim, and in the embryos of the latter animals 



by Peremeschko. In conclusion, we would point out that, owing to the 



Fig. 422. Cells from the spleeii 

 of man, the ox, and horse. 

 a-d, from m;m; a, free nu- 

 clei; b, ordinary cell (lymphoid 

 corpuscle) ; c, nucleated cell 

 with a blood corpuscle (?) in 

 the interior; d, with two such; 

 e, the same from the ox with 

 several; /, a cell from the 

 latter animal with fat-like 

 granules; g-h, from the horse ; 

 g, a cell containing several 

 fresh blood corpuscles and 

 granules, as in the last figure ; 

 h, cell with an agglomeration 

 of granules; i, the same, free; 

 *, a cell containing small 

 colourless molecules. 



