28 ORGANS OF DIGESTION. 



SECT. II. OF THE INTESTINAL CANAL. 



m 



The Intestinal Canal is from thirty to thirty-five feet in length, 

 and extends from the pylorus to the anus, Owing principally 

 to a well marked difference in magnitude, it is divided by ana- 

 tomists into the Small and into the Large intestine. 



Of the Small Intestine. 



The Small Intestine (Intestinum Tenue) commences at the 

 pylorus, and terminates in the right iliac region by a lateral 

 aperture into the large intestine. It is four-fifths of the length 

 of the whole canal, and measures from twenty-four to twenty- 

 eight feet.* When moderately distended its diameter is about 

 one inch. It retains from one end to the other an uninterrupt- 

 ed cylindrical shape, with the exception that if the two ends be 

 compared, the upper will be found larger than what is stated as 

 the medium measurement, and the lower smaller; or, in other 

 words, the intestine decreases successively from above down- 

 wards, and, as a whole, is slightly conoidal, though this diminu- 

 tion is so gradual that it is not perceptible in any short space. 



The Small Intestine, like the stomach, consists of four dis- 

 tinct coats, the peritoneal, the muscular, the cellular, and mu- 

 cous. 



The Peritoneal Coat is complete, and forms the external sur- 

 face. It is continued afterwards in two laminae from the intes- 

 tine to the lumbar vertebrae, thereby constituting the Mesente- 

 ry. The two laminae, where they depart from the intestine, are 

 loosely connected with each other, for the purpose of allowing 

 room for the dilatation of the intestine, on the same principle 

 which is exemplified in regard to the stomach. 



The muscular Coat is next to the peritoneal. Its fibres are 



* This is the generally received opinion of anatomists^ it would appear, how- 

 ever, to be a-pplicable only when the intestine is left attached to the mesentery; 

 for if it be cut off and straightened, it will measure thirty-four feet r which, added 

 to eight feet of large intestine treated in the same way, will amount in all to 

 forty-two feet. If to the estimate of this length we add what is lost by the 

 doublings of the mucous coat, the entire length of surface must amount to nearly 

 sixty feet, at least, in many subjects. 



