(LECUM AND VEKMIFOKM PEOCESS. 



1217 



of those over 60 years old, whilst it is unknown in the child. This frequency of occlusion, the 

 physiological atrophy which takes place after middle life, the great variations in length, and other 

 signs of instability, have been considered to point to the retrogressive character of the vermiform 

 process. 



A vermiform process is found only in man, the higher apes, and the wombat, although in 

 certain rodents a somewhat similar arrangement exists. In carnivorous animals the caecum is very 

 slightly developed ; in herbivorous animals (with a simple stomach) it is, as a rule, extremely large. 

 It has been suggested that the vermiform process in man is the degenerated remains of the 

 herbivorous caecum, which has been replaced by the carnivorous form. Another and perhaps 

 more probable view regards the process as a lymph organ, having the same functions as lymph 

 nodules, and, like these, undergoing degeneration after middle life (Berry). 



In the foetus and child, as well as in the adult with the infantile type of caecum, the vermi- 

 form process springs from the true apex, not from the medial and posterior aspect. 



FIG. 955. STRUCTURE OF THE VERMIFORM PROCESS. 

 A. From a child two years old. B. From a male, age 56. 



It will be observed that the tela submucosa is almost entirely occupied by lymph nodules and patches. The 

 lamina muscularis mucosae is very faint, and lies quite close to the bases of the intestinal glands. The 

 longitudinal layer of muscular fibres forms a continuous sheet. 



Foreign bodies, although reputed to find their way very easily into the vermiform process, are 

 rarely found there after death. On the other hand, concretions or calculi, formed of mucus, 

 faeces, and various salts, are often present (Berry). 



Structure (Fig. 955). The tunica serosa is complete, and forms a perfect investment 

 for the process. The tunica muscularis, unlike that of the rest of the large intestine, has a 

 continuous and stout layer of longitudinal fibres, which passes at the root of the process 

 into the three tsenise coli (Fig. 954). The layer of circular fibres is well developed. The 

 tela submucosa is almost entirely occupied by large masses of lymph tissue surrounded 

 by sinus-like lymph spaces. Owing to the large size of these lymph nodules, the areolar 

 tissue of the submucosa is compressed against the inner surface of the muscular coat, and 

 forms a well-marked fibrous ring, which sends processes at intervals between the lymph 

 masses towards the mucous membrane. These lymph nodules, which correspond to 

 solitary lymphoid nodules, have, owing to their great number, been almost completely 

 crushed out of the mucosa (in which they chiefly lie in the intestine) into the submucosa. 



The mucous coat corresponds to that of the large intestine in its general characters, 

 but the intestinal glands are fewer, and irregular in their direction ; the lamina muscularis 

 mucosse is thin and ill-defined ; it lies just internal to the lymphoid nodules of the sub- 

 mucosa, and immediately outside the base of the intestinal glands. Some few lymph 

 nodules lie in the mucous coat also. 



Blood-vessels of the Csecum and Vermiform Process (Fig. 954). These parts are 

 supplied with blood by the ileo-colic artery. This gives off, near the upper angle formed by the 

 junction of the ileum with the small intestine (a) an anterior ileo-ccecal artery, which passes 

 down on the front of the ileo-caecal junction to the caecum, and breaks up into numerous branches 

 for the supply of that part ; (6) a posterior ileo-ccecal artery, similarly disposed on the back ; and 

 i the artery for the vermiform process. The last-named branch passes down behind the ileum (Fig. 

 954), then enters the mesentery of the process, and running along this near its free border, sends off 

 several branches across the little mesentery to the process, before finally ending in it. The course 

 of the artery behind the ileum is said to render it subject to pressure from faecal masses in that 

 gut, and thus to predispose to an interference with the blood supply of the vermiform process, 

 and to morbid changes in it. 



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