124 



NORMAL HISTOLOGY. 





intimately related vascular channels, forms the splenic pulp, and as 

 the cylindrical or spherical masses of dense adenoid tissue ensheath- 

 ing the arteries, constituting the Malpighian corpuscles. 



The largest trabeculas support the branches of the splenic artery ; 

 on entering at the hilum, these twigs receive a strong fibrous invest- 

 ment, or adventitious 

 FIG. 151. 



sheath, which accom- 

 panies the vessel and 

 becomes gradually 

 reduced as the arte- 

 ries diminish in size ; 

 finally, this sheath 

 blends with the con- 

 nective-tissue frame- 

 work of the paren- 

 chyma. Many of 

 the smaller branches 

 of the splenic ar- 

 tery are deflected 

 from the trabec- 

 ulae and enter the 

 surrounding tissue, 

 where they become 

 ensheathed at irregu- 

 lar intervals by cy- 

 lindrical or spherical masses of dense adenoid tissue and constitute 

 the Malpighian corpuscles. The artery usually pierces the mass 

 somewhat eccentrically, sometimes, however, passing near the centre. 

 Numerous small twigs are distributed to the tissue composing the 

 corpuscles ; after forming a net-work they eventually open into the 

 channels of 'the pulp ; the main artery of the Malpighian corpuscle 

 has a similar destination. 



The form of these ensheathing masses of adenoid tissue varies in 

 different animals ; in some (guinea-pigs) the arteries are accompanied 

 throughout their entire course by a layer of lymph-cells, while in 

 others (man, cat) the investment is limited to irregularly spherical 

 masses ; between these extremes numerous intermediate forms exist. 

 The peripheral zone of the Malpighian corpuscle is usually denser 

 than the central part, an arrangement favoring the sharp demarca- 

 tion of the body from the surrounding looser parenchyma ; in man 

 the corpuscles are less clearly defined than in many lower animals. 



The splenic pulp, which makes up the larger part of the bulk of 

 the organ, consists of a loose net-work of slender bands and imperfect 

 septa, composed of delicate fibres and broad plate-like connective- 



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||.|y : ; 

 v \Ts8f& 



Section of human spleen cutting transversely a Malpighian cor- 

 puscle : a, section of the somewhat eccentrically situated artery ; 

 b, capillaries distributed to the tissue of the corpuscle; /, the sur- 

 rounding lymphoid tissue of the splenic pulp. 



