THE INTESTINES. 41 



Of the Intestines. 



The intestines form a continued canal from the pylorus to 

 the anus, which is generally six times the length of the subject 

 to which they belong.* Although the different parts & this 

 tube appear somewhat different from each other, they agree in 

 their general structure. The coats or lamina of which they are 

 composed, are much like those of the stomach, but the perito- 

 neum which forms their external coat does not approach them 

 in the same manner ; nor is it continued in the form of omentum 

 from the whole tube, their being only a certain portion of intes- 

 tine, viz. the colon, from which such a process of peritoneum is 

 continued. 



The Muscular Coat, like that of the stomach, consists of 

 two strata, the exterior of which is composed of longitudinal 

 fibres, which adhere to the external coat, and do not appear 

 very strong. The other stratum, consisting of circular or 

 transverse fibres, is stronger, as the fibres are more numerous. 

 It is observable that they adhere to the longitudinal fibres ; and 

 they seldom, if ever, form complete circles. 



The cellular substance immediately within the muscular 

 fibres resembles the nervous coat of the stomach in its firmness 

 and density. It is likewise so arranged as to form many 

 circular ridges on its internal surface, which support to a certain 

 degree the permanent circular plaits of the internal coat, called 

 valvulae conniventes. 



The inner surface of the internal coat has been commonly 

 compared to that of velvet, and the coat is therefore called 

 villous ; but there is certainly a considerable difference 



* This is a rule a long time admitted among anatomists, making the small 

 intestines twenty-four or twenty-eight feet in length, and the large intestines 

 about six more. Cruvielhier considers the small intestine on the average 

 about 20 feet in length, and the large, four to five feet. But this mode of mea- 

 surement is found to be totally defective when applied to comparative anatomy, 

 and Dr. Homer has found it applicable only to man, when the intestine is left 

 attached to the mesentery ; for, as he observes, " if it be cut off and straight- 

 ened, the small intestine will measure thirty-four feet, which, added to the eight 

 feet which the large intestine measures when treated in the same way, will 

 amount in all to forty-two feet. If to this estimate of the length is added what 

 is lost by the doubling of the mucous coat, the entire length of surface must 

 amount to nearly sixty feet, at least in many subjects." p. 



4* 



