SPLEEN. 



789 



sheaths at all are found on the smaller veins, 

 and on the larger they are chiefly found on 

 that side on which the arteries and nerves 

 which accompany them lie. Only the two 

 primary trunks of the veins which proceed 

 from the spleen have for a very short dis- 

 tance a complete sheath, while all the arte- 

 ries, even the finest, possess one; a con- 

 dition of which more will be said hereafter. 



The minute structure of the sheaths of 

 the vessels in man altogether correspond 

 with that of the partitions ; and this holds 

 good of animals generally. But I have 

 not been able to detect unstriped muscular 

 fibre in the sheaths in all those cases in which 

 I have found it in the trabeculae. In oxen 

 this is especially the case ; while, on the con- 

 trary, in pigs, &c., they are very plainly 

 present. 



Great difficulties oppose the inquiry con- 

 cerning the distribution of the vessels in the 

 spleen itself: since, Istly, injection or in- 

 flation of the vessels gives little result on 

 account of the delicacy of the organ ; and, 

 2dly, great difficulties are connected with the 

 microscopic examination of the organ. What 

 will be now adduced concerning it is espe- 

 cially the result of the latter method of in- 

 quiry, which, combined with fine preparations 

 by the knife, has seemed to me to be the 

 most fertile in results. 



When the main branches of the splenic 

 artery have entered into the spleen they 

 lie in their sheaths, each in company with 

 a vein, to which they are posterior and infe- 

 rior : they are in tolerably loose connection 

 with the sheath, and not unfrequently they 

 take a serpentine course. In their further 

 distribution they do not behave as arteries 

 generally do, which continually give off 

 smaller branches, but they divide immediately 

 into a quantity of different large and long 

 branches in the manner of a shrub ; of these 

 the larger branches go to the anterior, the 

 smaller to the posterior, margin of the organ. 

 Beside this, it is especially to be remarked of 

 the arteries of the spleen, that their different 

 branches form no anastomoses. Assolant 

 tied a branch of the splenic artery in a living 

 dog, and then allowed the spleen to return 

 into the cavity of the belly. The dog died 

 thirty hours after : much inflammation and 

 exsudation of a bloody serous fluid was found 

 in the belly, and the spleen was quite healthy; 

 only the part cut off from the circulation of 

 the blood was gangrenous, and, as it were, 

 separated from the sound part by a line of 

 demarcation. In contrast to this, Heusinger 

 tied all the branches of the splenic artery, one 

 only excepted ; upon dissection, the whole 

 spleen was found to be mortified, excepting 

 the part in which the artery not deligated 

 ramified. Also injections in an artery always 

 return solely by the corresponding branch of 

 vein; and they only fill that region of the 

 spleen in which the branch ramifies, never 

 passing over into any other. I am unable 

 from my own experience to pass any judg- 

 ment upon these data, and will therefore not 



impugn them ; but I may be allowed to doubt 

 whether the capillaries of the pulp are com- 

 pletely separated from each other, and am 

 more inclined to believe that, in consequence 

 of the anatomical circumstances of the pulp, 

 such a separation' must be considered as im- 

 possible ; since in the spleen we have before 

 us, not a gland with special lobes separated 

 from each other, but a parenchyma every- 

 where united. The above results of deli- 

 gation and injection by no means necessarily 

 imply an isolated course of the capillaries, 

 and are fully explained by the supposition 

 that the arteries possess no anastomoses. 



When the arteries have divided into small 

 vessels of 1 to 2-100ths of a line, they come 

 into contact with the Malpighian corpuscles 

 in the mode already described ; while they 

 are also connected to these by their sheaths. 

 According to Giesker, their final terminations 

 are coronal or pencil-shaped, radiating so as 

 to surround the Malpighian corpuscles, and 

 altogether enclose them ; then arriving at 

 the highest point of the vesicle, they return 

 upon themselves in the shape of a loop, course 

 back again as veins, and there meet together, 

 beneath the point whence the artery radiated, 

 to form a vein, which enters the same sheath 

 from which the artery emerged. At this 

 point the sheath divides into three to four 

 fibrous threads, which pass over on the 

 spleen corpuscles to the threads arising 

 nearest to them, and unite with these. If 

 we compare with this description of the 

 minute anatomy of the spleen that which is 

 considered most admissible by J. Miiller, the 

 next author after Giesker, we shall find very 

 considerable contradictions. J. Miiller finds 

 that the smallest branches of arteries partly 

 continue on the side of the corpuscles with- 

 out giving off branches to them, partly per- 

 forate either a portion or the whole of the 

 corpuscle, without in any instance leaving 

 any branches of the artery in its interior; 

 that these fine arterial branches pass through 

 the middle of the corpuscles, then con- 

 tinue on their coats, and then quit them 

 altogether ; and that if an artery in the 

 corpuscle divides into many branches which 

 never happens on the surface, but always in 

 the thickness of its coats these branches 

 leave it again, in order to ramify minutely in 

 the surrounding red pulpy substance of the 

 spleen, into which part especially all the fine 

 pencil-shaped ramifications of the arteries 

 pass.. The commencements of the veins 

 spring from these branches ; they are tolerably 

 large, anastomose frequently with each other, 

 and scarcely have a special coat as yet. If a 

 little piece of the pulp of the spleen be care- 

 fully examined, it will be seen that it is as 

 if cribriform, and constitutes as it were a net- 

 work of red partitions, the diameters of 

 which are larger than the interspaces and 

 canals existing between them. It is these 

 venous canals which give the cellular appear- 

 ance seen in inflation of the veins of the 

 pulp, and which, injected, form structures 

 resembling the corpora cavernosa of the 



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