THE SPLEEN. 1081 



their walls become much attenuated, lose their tubular character, and the cells of 

 the lymphoid tissue of which they are composed become altered, presenting a 

 branched appearance and acquiring processes which are directly connected Avith 

 the processes of the sustentacular cells of the pulp (Fig. 691). In this manner the 

 capillary vessels terminate, and the blood flowing through them finds its way into 

 the interstices of the reticulated tissue formed by the branched connective-tissue 

 corpuscles of the splenic pulp. Thus the blood passing through the spleen is 

 brought into intimate relation with the elements of the pulp, and no doubt under- 

 goes important chan.i 



After these changes have taken place the blood is collected from the interstices 

 of the tissue by the rootlets of the veins, which commence much in the same way 

 as the arteries terminate. Where a vein is about to commence the connective- 

 tissue corpuscles of the pulp arrange themselves in rows in such a way as to form 

 an elongated space or sinus. They become changed in shape, being elongated 

 and spindle-shaped, and overlap each other at their extremities. They thus form 

 t of endothelial lining of the path or sinus, which is the radicle of a vein. 

 On the outer surface of these cells arc seen delicate transverse lines or markings 

 which are due to minute elastic fibrillse arranged in a circular manner around the 

 sinus. Thus the channel obtains a continuous external investment, and gradually 

 becomes converted into a small vein, which after a time presents a coat of 

 ordinary connective tissue, lined by a layer of fusiform epithelial cells which are 

 continuous with the supporting cells of the pulp. The smaller veins unite to form 

 larger ones which do not accompany the arteries, but soon enter the trabecular 

 sheaths of the capsule, and by their junction form from four to six branches which 

 emerge from the hilum and. uniting, form the splenic vein, the largest radicle of 

 the vena porta. 



The veins are remarkable for their numerous anastomoses, while the arteries 

 hardly anastomose at all. 



The lymphatics originate in two ways i. e. a trabecular set and a perivascu- 

 lar set. The former run on the trabeculae and empty into the superficial network 

 of the capsule. The peri vascular is the deep set, rising in the lymphoid tissue 

 surrounding the arteries and forming Malpighian corpuscles. At first they have 

 no walls. They are seen to run with an artery in pairs and singly with each larger 

 vein, forming many anastomoses. Both sets join at the hilus (see page 1077). 



Surface Form. The spleen is situated under cover of the ribs of the left side, being sepa- 

 rated from them by the Diaphragm, and above by a small portion of the lower margin of the 

 left kins:. Its position corresponds to the ninth, tenth, and eleventh ribs. It is placed very 

 obliquely. "It is oblique in two directions, viz. from above downward and outward, and also 

 from above downward and forward" (Cunningham). " Its highest and lowest points are on a 

 level respectively with the ninth dorsal and first lumbar spines ; its inner end is distant about an 

 inch and a halt' from the median plane of the body, and its outer end about reaches the mid- 

 axillary line Quain . 



Surgical Anatomy. Injury of the spleen is less common than that of the liver, on account 

 of its protected situation and connections. It may be ruptured by direct or indirect violence, 

 torn by a broken rib. or injured by a punctured or gunshot wound. When the organ is enlarged 

 the eliaiK-e of rupture is increased. The great risk is haemorrhage, owing to the great vascu- 

 larity of the organ, and the absence of a proper system of capillaries. The injury is not. how- 

 ever, necessarily fatal, and this would appear to be due in a great measure to the contractile 

 power of its capsule, which narrows the wound and prevents the escape of blood. In caies 

 where the diasmosis is clear and the symptoms indicate danger to life laparotomy must be per- 

 formed : and if the haemorrhage cannot be stayed by ordinary surgical methods the spleen must 

 be removed. The spleen may become displaced, producing great pain from stretching of the 

 - and nerves, and this may require removal of the organ. The spleen may become enor- 

 mously enlarged in certain diseased conditions, such as ague, syphilis, valvular disease of the 

 heart, or without any obtainable history of previous disease. It may also become enlarged in 

 lymphadenoma as a part of a general blood-disease. In these cases the tumor may sometimes 

 till the abdomen and extend into the pelvis, and may be mistaken for ovarian or uterine 

 disease. 



The spleen is sometimes the seat of cystic tumors, especially hydatids. and of abscess. 

 These cases require treatment by incision and drainage : and in abscess great case must be taken 

 if there are no adhesions between the spleen and abdominal cavity, to prevent the escape of any 

 of the pus into the peritoneal cavitv. If possible, the operation should be performed in two 



