Hv INTESTINAL TRACT. 



furnished with a reddish-yellow and lobulated gland, which is more similar 

 to what is perceived in the higher forms of vertebrate animals. 



As to the common appearances of coecal appendages,* if we commence 

 our investigations among the osseous fishes, we see in some one or more 

 small ducts, each ending externally in a blind extremity ; these either 

 surround the commencement of the intestine just beyond the pyloric or 

 lower end of the stomach, or else spring from one of the sides of the first 

 part of the small intestine, along which they may be continued for some 

 little distance. We find in a single fish from one to upwards of a hundred 

 of these coecal appendages, each of which may open, by a separate .orifice 

 into the intestinal canal, or two or more conjoining form a common duct, 

 and thus diminish the number of openings, while in the bogue-fish (Boops), 

 two coecal appendages are seen at the termination of the intestinal tract. In 

 the sword-fish (Xiphias), all the various appendages conjoin with the common 

 tubes which empty their contents into the intestines. - Passing from the 

 osseous upwards to the cartilaginous or semi- cartilaginous fishes of the 

 ganoid sub-class, we • still find this gland present. Thus in the sturgeon 

 (Acipenser), a mass of areolar tissue binds the various coeca . together, 

 forming it into a parenchymatous conglomerate gland. 



The general appearance of the ccecal appendages consists of ducts of 

 varying .length and numbers, attached . externally to the small intestines, 

 into which they empty themselves. If these cceca are opened, they are mostly 

 seen to possess a glandular lining membrane, where a glairy fluid is secreted, 

 similar in appearance to the secretion from the internal surface of the 

 intestinal canal. Chyme has likewise been said to have been found 

 inside them - . It seems probable that in the interior of these tubes a 

 large amount of nutritive substances are present, for the tape-worms 

 (Bothriocephali) 'so common in some fishes, as the salmon, are almost 

 constantly found with their heads up these cceca, and from which they must 

 obtain their subsistence. For it is reasonable to suppose that in choosing 

 this locality they have been influenced by one of the following considera- 

 tions : — Absence from the main intestinal tract, which is constantly being 

 employed in conveying nutriment and excreta ; or else in selecting some 

 situation where the nutriment is more abundant. 



If we take a general survey of these two classes, we observe that coecal 

 appendages are far more common among marine than fresh-water fishes ; 



* It may be as well before proceeding further to explain my plan for examining these appendages, 

 for I employ, as a rule, one of the following processes. The easiest mode is to tie the 03sophagus 

 and inflate the intestines, appendages, and stomach by means of a blowpipe, tube, or quill, from 

 an opening made in the intestines, or to tie the intestines and inflate from the oesophagus, while 

 the use of a solution of chromic acid hardens the preparation. Should the fish not be sufficiently 

 fresh for this purpose, it must be examined .under water, when occasionally it can be injected with 

 spirit. 



