2l6 INTESTINAL DIGESTION 



intestine. Later, following the observations of Thiry (1864), the intes- 

 tinal juice was obtained by what is known as the Thiry-Vella method. 

 The experiment of Thiry, modified by Vella, is the following : The ab- 

 domen of a dog is opened and a portion of the small intestine, twelve 

 to twenty inches (30 to 50 centimeters) in length, is cut away from the 

 rest of the tract. The two cut ends of the intestine are then connected, 

 leaving a portion isolated but attached to the mesentery, each end of 

 which is connected with an opening in the abdominal walls so as to 

 leave two fistulous openings. The parts are then allowed to heal, and 

 what is supposed to be pure intestinal juice may be collected from the 

 isolated portion. While it must be admitted that this is an imperfect 

 way of obtaining a normal secretion, the observations are of consider- 

 able value. The result of these experiments has been to show that the 

 intestinal secretion inverts cane-sugar into dextrose and levulose (invert- 

 sugar) and may have a like action on milk-sugar and maltose. The 

 majority of observations have failed to show any action on starch or 

 fats. The ferment acting on the sugars has been called invertin 

 (Paschutin). 



PANCREATIC JUICE 



The pancreas is situated transversely in the upper part of the ab- 

 dominal cavity and is closely applied to its posterior wall. Its form is 

 elongated, presenting an enlarged thick portion, called the head, which 

 is attached to the duodenum, a body and a pointed extremity, which 

 latter is in close relation to the hilum of the spleen. Its average weight 

 is four to five ounces (114.4 to 141.7 grams); its length is about 

 seven inches (17.78 centimeters); its greatest breadth, about an inch 

 and a half (3.81 centimeters); and its thickness, three-quarters of an 

 inch (1.91 centimeters). It lies behind the peritoneum, which covers 

 only its anterior surface. 



There are nearly always, in the human subject, two pancreatic ducts 

 opening into the duodenum ; one which opens in common with the 

 ductus communis choledochus, and one which opens about an inch 

 (25.4 millimeters) above the main duct. The main duct is about an 

 eighth of an inch (3.2 millimeters) in diameter and extends along the 

 body of the gland, becoming larger as it approaches the opening. 

 The second duct is smaller and becomes diminished in calibre as it 

 passes to the duodenum. In general appearance and in minute struc- 

 ture, the pancreas nearly resembles the parotid. It differs, however, 

 from the salivary glands in some important particulars. It is rather 

 softer and looser in texture and has no distinct fibrous covering. Its 

 alveoli contain secreting cells, but here and there are found groups 



