THE DIGESTIVE SYSTEM. 577 



to uiidergo secondary degenerative or metaplastic changes. ' The mixed 

 parotid tumors differ in many respects from those elsewhere in the body 

 and in ways which suggest an origin in congenital malformations. More 

 recent studies indicate that many cell forms formerly interpreted as en- 

 dothelial are epithelial." 



Fibro-sarcoma and melano-sarcoma have been described. 



A case of rhabdomyoma of the parotid gland, with evidences of atypi- 

 cal development of portions of the gland, has been described. 3 Primary 

 carcinoma of these glands is rare. 



The Pancreas. 



Malformations and Displacements. 



The pancreas may be entirely absent in acephalous and double monsters. The pan- 

 creatic duct may be double; it may open into the duodenum at some distance from the 

 biliary duct, or into the stomach. The head of the pancreas may be unduly developed 

 and sometimes even completely separated from the rest of the organ, opening into the 

 duodenum with a duct of its own. Occasionally there is a small accessory pancreas 

 situated beneath the serosa of the duodenum or stomach. 



The pancreas is so firmly bound down that its position is not often changed. Some- 

 times, however, it is found pressed downward by tight lacing, displaced by aneurisms, 

 or contained in umbilical and diaphragmatic hernia?. 



ATROPHY, DEGENERATION, AND NECROSIS. 



Atrophy of the pancreas may occur in old age and as a result of press- 

 ure from tumors or other adjacent structures, and may be associated with 

 fatty infiltration. It occurs in a certain proportion of cases of diabetes 

 mellitus. 



Auto-digestion of portions of the pancreas, intra vitam, has been de- 

 scribed, and may, it is believed, lead to localized formation of fibrous 

 tissue in the organ. 4 



Albuminous Degeneration may occur in acute infectious diseases. The 

 organ may be red, swollen, and oedematous. The most marked minute 

 lesions are swelling and albuminous degeneration of the gland epithelium 

 with hypersemia and interstitial oedema. 



Fatty Degeneration may follow albuminous degeneration and is most 

 common in poisoning, especially by phosphorus. 



Fatty Infiltration, which should be distinguished from fatty degenera- 

 tion, consists in the accumulation of fat in the interstitial tissue of the 

 gland (Fig. 351). This when excessive may be associated with almost 

 complete atrophy of the gland structures. Under these conditions the 

 outline of the organ may be preserved, the fat being enclosed by the 

 capsule. 



1 Volkmann, Deutsche Zeits. f. Chir., Bd. xli., p. 61. 



2 For a critical study of the mixed tumors of the salivary gland see Wood, Ann. of 

 Surgery, vol. xxxix., 1904, p. 57, bibl. 



3 Prudden, "Rhabdomyoma of the Parotid Gland," American Journal of the Medi- 

 cal Sciences, April, 1883. 



4 Ohiari, Prager med. Wochenschrift, vol. xxv., No. 14, 1900. 



37 



