The pancreas has the structure of a salivary gland, consisting of glandular acini whose ducts communicate with a main duct lying in the centre of the gland (Wirsung's duct) and opening into the duodenum in common with the ductus choledochus.

The function of the pancreas seems to be similar to that of the salivary glands, but the gland possesses two pathological relations, which have not yet obtained a full explanation but are of great importance. These are the relations of the organ to the absorption of fat in the alimentary canal, and to the occurrence of diabetes. Extirpation of the pancreas seems to hinder the absorption of fat, and disease of the organ which causes destruction of the tissue or obstruction of the duct seems to have a similar effect, so that fat appears abundantly in the faeces. The relation of the pancreas to diabetes has been already referred to at pp. 272 and 273.

Malformations occur chiefly in the form of supernumerary or accessory glands. These are usually situated in the wall of the stomach, duodenum, or jejunum. Another malformation is that in which the pancreas surrounds the duodenum.

The pancreas is occasionally the seat of Haemorrhages into its substance (Pancreatic apoplexy). These may be the result of injuries to the abdominal wall or the consequence of passive hyperemia in diseases of the heart, lungs, or liver. Some cases of sudden death have been recorded by Zenker, Hooper, and Klebs, in which the most obvious lesion was haemorrhage into the substance of this gland. No cause for the haemorrhage was apparent. It is supposed that the lesion caused pressure on the neighbouring cceliac plexus and semilunar ganglion and a consequent reflex paralysis of the heart, just as paralysis of the heart is producible by blows on the abdomen (Goltz's experiment). The haemorrhage may lead later on to abscess of the pancreas which sometimes bursts into the peritoneum.

Inflammations of the pancreas are of various kinds. Besides the abscess just mentioned we have suppurative pancreatitis like suppurative parotitis, resulting in abscesses; also indurative interstitial inflammation with loss of gland tissue, this condition being sometimes of syphilitic origin.

Atrophy of the pancreas is observed often as a part of general emaciation, but it has been found in a good many cases of Diabetes mellitus.

Fatty infiltration of the pancreas is one of the commonest lesions of this gland. There is normally some adipose tissue in the midst of the gland, and this sometimes undergoes considerable increase, the proper glandular substance becoming atrophied, and adipose tissue taking its place, the shape and general appearance of the gland being preserved. The condition may be part of a general obesity, or it may occur in old age, and, in this latter case, it may be presumed that atrophy of the glandular tissue is the first condition, the adipose tissue developing afterwards, as in fatty infiltration of voluntary muscle. Necrosis sometimes occurs in the adipose tissue of the organ, producing opaque yellow patches of a striking character. •

The glandular structure sometimes undergoes Cloudy swelling, in common with that of the liver and other organs in the acute fevers. Fatty degeneration is also met with.

Tuberculosis is not common in the pancreas, but we meet with caseous masses having the characters of a local tuberculosis. More frequently the pancreas is involved secondarily in a tuberculosis arising in neighbouring lymphatic glands. Syphilitic Gummata have been observed.

Of the tumours of the pancreas, Cancer is by far the most important. It occurs most frequently in the head, rarely in the body or tail. It is mostly a dense tumour of fibrous appearance (scirrhus), but cases of soft and 01 colloid cancer have been seen. The cancer often obstructs Wirsung's duct, or produces still more serious results by obstructing the ductus communis. It may even by its retraction or by its prominence cause a partial obstruction of the duodenum. There may arise in this way considerable disturbances from the continuous extension of the tumour. We may also have secondary tumours in the lymphatic glands, liver, or peritoneum.

Cancers of the stomach or duodenum rarely extend to the pancreas. The gland is sometimes the seat of secondary metastatic tumours when the disease becomes generalized.

The Pancreatic duct (Wirsung's) is liable to certain changes. Concretions occur in it, comparable to those of the salivary glands. They are mostly round or oval and white or greyish white. In size they have been met with as large as a hazel nut or larger, but they are usually small like grains of sand. They are composed chiefly of carbonate and phosphate of lime. They very often arise in dilated ducts, but if large may cause dilatation by obstructing the duct.

Obstruction and Dilatation of Wirsung's canal may arise, as we have seen, from calculi, cancers of the head of the pancreas, or from tumours in the neighbourhood. Dilatation also occurs secondarily to atrophy of the gland. The dilated duct forms a series of pouches, or else there is a more definitely localized dilatation so that actual cysts are formed. The latter will occur when the orifice is completely obstructed; the cysts may reach the size of the fist or that of a child's head, and these are sometimes designated Ranula pancreatica. The contents of the dilated duct may be simply the fluid secretion, but sometimes there is thickening of the contents and even haemorrhage. In this way we may have coagula causing the cysts to look like aneurysms, all the more as the lining of the cyst may become the seat of calcareous plates like the internal coat of an artery in aneurysm.

Literature

Klebs, Handb. der path. Anat., i., 1876; Friedreich, in Ziemssen's Cycl., vii. Relation to fat absorption - Harlem, (literature) Journ. of Pbys., xviii., 1895. Malformations - Symington, Jour, of anat. and phys., xix., 18S5; Klob, Zeitschr. d. Wien. Aerzte., 1859; Zenker, Virch. Arch., xxi. Haemorrhage - Prince Morton, Boston Med. and Surg. Jour., 1882; Zenker, Berl. klin. Wochenscb., 1874; Challand, Bull, de la Soc. med. de la Suisse rom., 1877; Klebs, 1. c.

Atrophy And Diabetes

Klebs, 1. c; Frerichs, Ueber den Diabetes, 1884; Duffey Dubl. Jour, of Med. Sc, 1884; Israel, Virch. Arch., lxxxiii., 1881. Concretions - Johnston, Amer. Jour, of Med. Sc, 1884. Cysts - Recklinghausen, Virch. Arch.,, xxx.; Hjelt, Schmidt's Jahrb., clvii., 1873.