80 PRACTICAL HISTOLOGY. 



the form of a continuous tube, and at the same time they become more spindle-shaped. This 

 is the mode of origin of a venous radicle from the pulp, so that the spaces in the splenic pulp 

 are directly continuous with the vascular system. {Indicate these details in PL XVIIL, Fig. 2.) 



BLOOD-VESSELS OF THE SPLEEN. 



The splenic artery enters the organ (at the hilum) along with the vein, lymphatics, and 

 nerves, all of which are imbedded in the connective tissue, which becomes continuous with the 

 splenic trabeculse. It runs for a short distance in these trabeculae, but it soon leaves the vein, 

 and its branches divide suddenly into a large number of smaller branches (fenicillf). The small 

 branches soon become more or less completely ensheathed by a solid mass of adenoid tissue, 

 and this tissue constitutes the so-called Malpighian or splenic corpuscles. These are supplied 

 by distinct capillaries, which form a uniform network with wide meshes. Other arterial 

 branches open directly into the meshwork, or ' honeycombed matrix,' of the splenic pulp, 

 which, as above described, opens into the rootlets of the veins (venous sinuses), and these 

 again into the larger venous trunks lying in the trabeculae. No capillaries are found in the 

 pulp ; they are confined to the Malpighian corpuscles. At the periphery of these corpuscles 

 the capillaries open directly into the spaces of the pulp, which are therefore the channels of 

 communication between the terminations of the arteries and the origin of the venous radicles. 

 The blood-stream in the splenic pulp, therefore, corresponds to the lymph-stream in a 

 lymphatic gland. 



PREPARATION. Injection of the Blood-vessels of the Spleen, (a) Carmine Gelatine Mass. 

 It is well to use a constant-pressure apparatus, and to cease injecting whenever the mass 

 ceases to flow into the spleen. Inject from the splenic artery a thin carmine gelatine mass. 

 If the human spleen be taken, select the spleen of a child. After the injection is completed 

 harden the organ in Miiller's fluid. The spleen of a rat does very well, but in all cases the 

 animal ought to be killed by bleeding. In the case of animals it is sometimes advantageous 

 to wash out the blood-corpuscles of the spleen with a stream of salt solution before using the 

 gelatine mass. 



(b) Silver Nitrate Injection. Wash out the blood-vessels with distilled water, and then 

 throw in a quarter per cent, solution of silver nitrate. Harden in alcohol. Sections of this 

 show the endothelium of the venous sinuses. 



Make sections of the above, stain them with logwood, and mount them in dammar. 



EXAMINATION (L). Observe the Malpighian corpuscles ; oval or irregularly shaped 

 bodies stained blue, and in each note a branch of the splenic artery and a few capillaries. 

 The pulp contains a network of spaces (venous sinuses), filled with the red carmine mass, and 

 in this lie the masses of logwood-coloured ' pulp ' of the spleen, which are about the same 

 breadth as the venous or cavernous sinuses. Larger spaces the rootlets of a vein may 

 be seen opening directly into these spaces. (Indicate the blood-vessels in one half of P\. XVIII., 

 Fig. i.) 



(H). Note the network of spaces filled with the red mass, and between them the lymph- 

 cells stained blue. Select a venous radicle, and note the layer of endothelium lining it. Trace 

 the continuation of an intra-Malpighian capillary into the red network at its margin. 



NERVES OF THE SPLEEN. 



These have already been alluded to (p. 45). Amongst the non-medullated nerve-fibres, I 

 have found a large number of ' plasma-cells ' (p. 20). 



