of the Fishery Board for Scotland. 



45 



I have no doubt that an investigation of the stomachs of a series 

 of animals would yield data that would throw much light on the ques- 

 tion of digestion in the higher animals. These glands of the cardiac 

 sac appear to me to present all the characters of the 'glands of the 

 1 fundus ' of the mammalian stomach, minus the inner layer of cells. On 

 this view, morphologically the so-called cardiac sac or crop would be 

 homologous with the cardiac end and fundus of the human stomach. 



The Pyloric Sac or Stomach. 



By the term ' pyloric sac' or 1 stomach ' is meant that short tubular organ 

 with thick muscular walls opening from the crop, and continued into the 

 intestine. Professor Huxley speaks of it as resembling a gizzard, from 

 the thickness of its muscular coat, which is several times thicker than the 

 corresponding coat of the crop. Moreover, it is always firmly contracted 

 around its contents. 



The surface of the mucous membrane consists of a number of large 

 irregular depressions, which we may regard as crypts. These crypts 

 are deeper than those in the cardiac sac. Owing to their depth, and 

 from their being bounded on all sides by a rampart or mucous fold, they 

 may be regarded simply as mucous crypts or glands \ sometimes they are 

 much branched. 



The pyloric sac is always lined by a very thick coating of mucus, which 

 in hardened specimens assumes a membranous form. It lies not only on 

 the surface, but dips down into the pyloric crypts or glands. 



The structure of the mucous membrane is comparatively simple. PI. II. 

 fig. 1, shows a vertical section of the coats of this organ. The sub-mucous 

 coat (s.m.) sends up some large folds and some smaller ones into the 

 mucous coat, the smaller ones form the boundaries of the glands or crypts, 

 seen here in vertical section, while glands are arranged on the sides of 

 the larger folds. The surface of the pyloric sac and the glands or crypts 

 are lined throughout by a single layer of tall narrow columnar epithelium, 

 which presents all the characters of the epithelium lining the gland ducts 

 and surface of the cardiac sac. The nucleus is placed deep in the cell, 

 while the upper part is clear, open at the mouth, and filled with mucus. 

 The layer of mucus which lies over the mouths of these crypts is shown 

 in figs. 1 and 2 I. Not unfrequently one finds a section of an intes- 

 tinal worm embedded in the mucous covering. There is no muscularis 

 mucosae. The circular muscular coat is very thick, while the longi- 

 tudinal is thin. Pig. 2 shows an enlarged view of one of the larger 

 folds, with its lateral secondary depressions, giving rise to the appearance 

 of glands, many of them with branches. Structurally this organ is 

 comparable with the pyloric end of the mammalian stomach, and 

 the crypts seem to me to be analogous to the pyloric glands. They 

 present much the same characters, although I did not find that the cells 

 in the deeper part of the crypts differed in appearance from those lining 

 the upper part of the gland or crypt. 



I reserve the consideration of the structure of the other parts of the 

 digestive tract for another occasion. 



My thanks are due to Mr Couper, fishery officer at Aberdeen, for the 

 trouble he took in selecting fish suitable for these researches. 



