194 MICROSCOPIC ANATOMY OF THE ORGANS. 



islands of Langerhans. Their structure has been described by 

 E. L. Opie. According to him, they are most numerous in 

 the splenic end of the pancreas. He describes them as " com- 

 posed of cells having the same origin as those of the glandular 

 acini," and richly supplied with blood capillaries. In injected 

 specimens the capillaries stand out from the surrounding tissues 

 like a glomerulus. It has been shown fairly conclusively that 

 the islands of Langerhans have to do with the internal secre- 

 tion of the gland and the control of the storing up and 

 excretion of sugar (Opie). 



The framework of the pancreas consists of a network of white 

 and elastic connective-tissue fibres. The interlobular septa 

 contain blood-vessels and ducts, which, however, do not run 

 side by side, as in the salivary glands, but enter the gland and 

 the lobules at different points (Flint). The lobules are marked 

 off by interlacing connective-tissue fibrils, and with these the 

 basement membranes surrounding the acini are continuous. 

 The lobules are polyhedral in shape, but do not possess a 

 hilus, as in the salivary glands. The framework of the 

 islands of Langerhans is made up of fine interlacing fibrils 

 supporting the groups of cells and the capillaries. This 

 structure is shown in a drawing by Flint (Fig. 149). 



The nerves of the pancreas are almost entirely non-medul- 

 lated. They enter the gland with the arteries and ramify 

 between the epithelial cells of the alveoli. Small ganglia have 

 been observed in their course. 



G. LIVER. 



The liver is a compound tubular gland in which the tubules 

 are joined by numerous anastomoses. It consists of many 

 lobules, which are separated by a continuation into the gland of 

 the connective tissue of the capsule of Glisson, which surrounds 

 the whole organ. This is known as the interlobular connective 

 tissue. The lobules have the form of rounded or polygonal 

 prisms, and in section appear usually as polygonal fields, which 

 in some animals (pig, camel) are marked off very definitely by 

 a strongly developed connective-tissue framework (Fig. 150). 



