INTESTINUM TENUE. 1177 



the portal vein. These veins contain numerous valves which, though competent to prevent the 

 return of blood in the child, are rarely so in the adult. 



The lymph vessels of the .stomach arise in an extensive plexus in the mucous membrane 

 around the gastric glands. They then join a plexus of vessels in the tela submucosa, from which 

 some vessels pass at intervals to join another plexus of vessels, subserous in position ; piercing 

 the muscular coats obliquely in their course. The efferent vessels pass mainly from the subserous 

 plexus, and are arranged in three main groups, which pass in different directions, and drain 

 three different areas of the stomach wall 



One set of vessels is connected mainly with the whole of the lesser curvature, from fundus 

 to pylorus, and the adjacent half or two-thirds of the anterior and posterior surfaces of the 

 stomach. These vessels pass to the superior gastric glands, along the lesser curvature, and, in 

 company with the left gastric artery, to the cceliac glands. 



The second set of vessels drains an area which includes the greater curvature below the 

 fundus, and the adjacent portions of the anterior and posterior surfaces of the stomach. These 

 vessels pass with the right gastro-epiploic artery to some inferior gastric glands which lie below 

 and behind the pylorus, and thence they pass with the hepatic artery to the coeliac glands. 



The third set of vessels drains the region of the fundus. The vessels from this area pass in 

 the gastro-lienal ligament to the spleen, where they are connected with some splenic glands, 

 and pass onwards, along the superior border of the pancreas, to the coeliac glands also. 



The superior and inferior gastric glands and the splenic glands are the first glands interposed 

 in the course of the lymph vessels. The coeliac glands form the second set. 



The nerves are derived from the two vagus nerves and from the cceliac ganglia of the 

 sympathetic. The vagi nerves pass through the diaphragm with the oesophagus, the left 

 lying on its anterior, the right on its posterior aspect ; in this way they reach the anterior and 

 posterior surfaces of the stomach respectively. Here they unite with the sympathetic fibres from 

 the coeliac plexus, which pass to the stomach with the branches of the coeliac artery. The nerve 

 fibres, which are chiefly non-medullated, form two gangliated plexuses, those of the myenteric 

 plexus and the submucous plexus, in the muscular and submucous coats respectively. 



The development of the stomach is described with that of the intestines on pp. 47 and 1249. 



INTESTINUM TENUE. 



The small intestine is the portion of the digestive tube which is placed 

 between the stomach and the beginning of the large intestine. It commences at 

 the pylorus, where it is continuous with the stomach, and ends at the valvula 

 coli by joining the large intestine. It occupies the greater portion of the 

 abdominal cavity below the liver and stomach (Fig. 913), and is found in the 

 umbilical, hypogastric, and both lumbar regions ; also, but to a less extent, in the 

 other regions of the abdomen, and in the pelvic cavity. 



In length, the small intestine usually measures over 20 feet. According to 

 Treves, it is 22 J ft. in the male, 23 in the female, whilst Jonnesco gives the average 

 length at 24 ft. 7 ins., or 7J metres. In form it is cylindrical, with a diameter 

 varying from nearly two inches (47 mm.) in the duodenum to a little over an inch 

 (27 mm.) at the end of the ileum ; there is thus a gradual diminution in its size 

 from the pylorus to the valvula coli. 



The small intestine is relatively longer in the child than in the adult ; at birth it is to the total 

 height of the child as 7 to 1, whilst in the adult the proportion is as 4 to 1. Notwithstanding 

 Treves' results, it is generally held that the small gut is relatively longer in the male than the 

 female. 



While the former figures, 20 to 22 feet, represent the entire length of the intestine in its most 

 extended form, after death, when muscular tonus has disappeared, it is probable that during life 

 the length is not so great. The muscular coats, both longitudinal and circular, are more or less 

 contracted, and probably the total length during life may be estimated as 15 to 17 feet. 



In formalin-hardened bodies the small bowel rarely measures more than 12 or 13 feet in 

 length. Similarly its diameter is often reduced in places to or inch (12 '5 to 187 mm.), 

 although the greater part of the gut may retain its usual width : these narrow parts have 

 apparently been fixed in a state of contraction. 



The small intestine is divided more or less arbitrarily into three parts (Fig. 873) 

 namely, the duodenum, constituting the first eleven inches, distinctly marked off 

 from the rest by its fixation and the absence of a mesentery ; the intestinum jejunum 

 ("empty intestine") which comprises the upper two-fifths, and the intestinum 

 ileum (" twisted intestine ") the lower three-fifths of the remainder. The jejunum 

 and ileum pass imperceptibly into one another, and the line of division drawn between 

 them is entirely artificial; however, if typical parts of the two namely, the 

 beginning of the jejunum and the end of the ileum are selected, they differ so 



