144 



INTRODUCTION. 



With regard to the proportionate length of the intestinal canal, as 

 compared with that of the body, it is, in Man, as about seven to one ; 

 in the Chimpanzee, as about six to one ; in the Simiae, generally, as 

 six or eight to one ; in the Carnivora, as three, five, or eight to one ; 

 in the Ruminantia, as eleven, or even twenty-eight to one ; in the Pachy- 

 dermata, as six, eight, or ten to one : in the Hyrax the intestinal canal 

 measures nine feet four inches, being six times the length of the head 

 and body. 



In the Rodentia the length of the intestine varies with regard to the 

 body, but greatly exceeds it in all : in the Coipus the total length of 

 the intestine, including the caecum, is twenty-two feet six inches, the 

 head and body of the animal being one foot eleven inches, which is 

 about eleven to one : in Octodon it is as about seven and a half to one : 

 in the Seals it is as fourteen or fifteen to one. 



Estimates of this kind, however, are not to be trusted, and are really 

 of less value than is imagined: the anatomist has to regard the capacity, 

 the valvulae, and the sacculi of the intestines, conditions of structure, 

 which affect, materially, the extent of their inner surface, and for which 

 it is difficult to make due allowance ; but yet, without taking these con- 

 ditions into the calculation, the result cannot but be unsatisfactory in the 

 extreme : for it must be evident, that a very slender intestine, of great 

 length, may have a much inferior extent of inner surface to that of a 

 shorter intestine of greater volume, studded with elevated villi, furnished 

 with valvulae conniventes, or puckered into bold sacculi. The following 

 sketches represent the mucous lining of the duodenum of the Porpoise, 



141 



142 



disposed in longitudinal folds (fig. 140) ; that of the small intestines of 

 the Bear, with its beautiful villous surface (fig. 141); and that of the 

 human colon, forming deep transverse valvulae (fig. 142). 



