There is no proper capsule to the pancreas : the areolar tissue which invests it does so very unequally in different parts, and is strictly continuous on the one hand with that which attaches it to neighbouring parts, and on the other with that which penetrates between its lobules to the internal parts of the organ. On the anterior surface tiiis areolar tissue is so deficient that the structure of the gland is in no way concealed by it.
Internal On cutting into the pancreas, we see that it is the same through out its mass as it is on its surface ; that it is solid and homorrencous ; that one part exactly resembles anotrier ; that there is the same aggregation of the acini into lobules and of lobules into lobes, and the same nesting in capsules of areolar tissue by the elasticity of which the acini and lobules are made to pro trude from the cut surface, whereby it be comes granulated and nodular ; and this irregularity of surface is ahnost the only difference between the appearance of a section and that of the external surface as just now described. A good idea of the absolute and relative size of the different elements may be obtained by a section : the lobes may be said to have an average diameter of 4. of an inch ; the lobules --A, or of the lobes ; the acini ,J7 of an inch* ; but all the measurements are liable to the greatest variety.
The areolar tissue, less abundant than in the salivary glands, consists almost entirely' of the white fibrous element, and the areoI are very lax and large : it is most abundant near the centre of the gland around the duct, and about the head of the pancreas, where it forms a firm and intimate union between the gland substance and the duodenum.
The duct of the pancreas, which has been called the canal of Wirsung, from its dis covery by that anatomist in the year 1642, passes from left to right throughout the en tire length of the organ, beginning within a few lines of its splenic extremity, by the union, at an acute angle, of two or more minute ramusculi, and emptying itself into the duodenum at or near the junction of its vertical and inferior-horizontal portions. Its course is somewhat sinuous ; it lies, on the average, about equidistant between the upper and lower margin, but nearer the pos terior than the anterior surface. It is alto gether concealed by the gland structure, even its point of entrance into the wall of the intestine. After originating in the manner described, it receives continuously in its course small branches which enter it at right angles, and which, unlike the main duct, are perfectly straight and not sinuous, and mostly single and unbranched, each coming from its own appropriate lobe, without receiving any accessory branches from neighbouring ones ; so that they look, as Cruveilhier has said,"like the legs of a centipede, of the which the main duct forms the body. By these tributary
ducts the calibre of the main canal is gradu ally increased till it reaches a diameter, at the right extremity of the gland, of -kth of an inch. It is of an opaque white, and there fore easily distinguishable from the gland substance. Its walls are thin and elastic, but dense and firm. It) the tenuity or its walls it stands in strong contrast with the ducts of the salivary glands ; but, like them it is con tinuous, by its external loose fib'rous coat, with the areolar tissue of the gland. Just before entering the intestine the duct com monly receives a large tributary branch, often nearly as large as itself, cotning from the head of the pancreas. This occasionally remains permanently distinct, and opens into the in testine by a separate orifice (see fig. 55. B, c), a condition always present, according to Meckel, in the early. fcetus, so that this irre gularity is essentially nothing but au exten sion of a fcetal condition into adult life. When this duplicity of orifice exists, the separate duct from the head of the pancreas has its own little papilla, proportionately smaller than the normal one, and separated from it about iths of an inch or an inch. It is usually lower dow n, though sometimes higher up, than the main orifice. It has been ob served by Cruveilhier, that when there is one duct opening by a distinct orifice appropriated to itself alone, there is always another open in," into the duodenum in the normal way in 0 common with the ductus choledochus. Ac cording to other authorities*, however, the pancreatic duct and the bile duct will sotne times open on the mucous membrane of the duodenum by two entirely distinct orifices, when the former is single and there is no secondary one, as seen in fig. 55. c. Oc casionally the pancreatic duct is double throughout its whole length, the two running side by side and communicating, just before thtir junction, with the ductus choledochus, as shown in fig. 55. D. Scemmerring asserts that there are sometimes three ducts dis tinct throughout and opening separately. All the varieties of method of termination of the pancreatic duct have been collected and ana lysed by Tiedemann*; and he has come to the interesting conclusion that they all have their analogues in the different arrangements found in the various species of the lower animals.