BLOOD-VESSELS OF THE SPLEEN. 



149 



for them. These corpuscles consist of adenoid tissue, 

 corpuscles, and they present exactly the same structure 



whose meshes are filled with lymph- 

 as the solitary follicles of the intestine 

 ( 197). They are small lym- 

 phatic accumulations around 

 the arteries peri-arterial 

 masses of adenoid tissue similar 

 to those masses that occur in a 





Fig. 120. 



Trabecular of the spleen of a cat with the splenic pulp washed 



out. a, trabecula ; b, vein. 



Fig. 121. 



Adenoid reticulum of 



spleen of cat. 



slightly different form in other organs, e.g. , the lungs. In a section of the spleen the artery 

 may pass through the centre of the mass or through one side of it, and in some cases the tissue 

 is collected unequally on opposite sides of the vessel, so that it is lob-sided. They are not 

 surrounded by any special envelope. In some animals the lymphatic tissue is continued for some 

 distance along the small arteries, so that to some extent it resembles a peri-vascular sheath of 

 adenoid tissue. In a well-injected spleen, a few fine capillaries are to be found within these 

 corpuscles. The capillaries distributed in the substance of the Malpighian corpuscle (fig. 122) 

 form a network, and ultimately pour their blood into the spaces in the pulp. According to 

 Cadiat, the corpuscles are separated from the 

 splenic pulp by a lymphatic sinus, which is 

 traversed by efferent capillaries passing to the 

 pulp (fig. 122).] 



Connection of Arteries and Veins. It is 

 very difficult to determine what is the exact 

 mode of termination of the arteries within the 

 spleen, more especially as it is extremely diffi- 

 cult to inject the blood-vessels of the spleen. 

 According to Stieda, and others, the fine 

 "capillary arteries" formed by the division 

 of the small arteries do not open directly 

 into the capillary veins, but the connection 

 between the arteries and veins is by means of 

 the "intermediary intercellular spaces" of 

 the reticulum of the spleen, so that, according 

 to this view, there is no continuous channel 

 lined throughout by epithelium connecting 

 these vessels one with another. Thus the 

 blood of the spleen flows into the spaces of the 

 adenoid reticulum just as the lymph-stream 

 flows through the spaces in a lymph-gland. 



Fig. 122. 



According to Billroth and kolhker, a closed Malpighian corpuscle of a cat's spleen injected, 

 blood-channel actually does exist between the a artery . b) meghes of the pulp in j e cted ; 

 capillary arteries and the veins, consisting c? the artery of the corpil scle ramifying in the 

 of dilated spaces (similar to those ot erectile i ymp hatic tissue composing it. 

 tissue). These intermediary spaces are said to 



be completely lined by spindle-shaped epithelium, which abuts externally on the reticulum of 

 the pulp. [According to Frey, owing to the walls of the terminal vessels being incomplete, 

 there being clefts or spaces between the cells composing them, the blood passes freely into 

 spaces of the adenoid tissue of the pulp ' ' in the same way as the water of a river finds its way 

 amongst the pebbles of its bed," these "intermediary passages" being bounded directly by 

 the cells and fibres of the network of the pulp. From these passages the venous radicles arise. 

 At first, their walls are imperfect and cribriform, and they often present peculiar transverse 

 markings, due to the circular disposition of the elastic fibres of the reticulum. The small veins 

 have at first a different course from the arteries. They anastomose freely, but they soon become 

 ensheathed, and accompany the arteries in their course.] 



