16 THE STRUCTURE OF THE GLANDS OF BRUNNEB 



per cent, solution of potassium carbonate, or a saturated solution of barium hydroxide, 

 the substance in the cells of the glands of Brunner slowly dissolved. The various 

 stages of this slow solution could be determined by treating sections from time to time with 

 strong muchaematein. The procedure is as follows : A number of sections fastened to 

 slides by the water method are freed from paraffin, passed through alcohol to water, 

 placed in a Coplin jar containing a quantity of the solution to be tested and the whole 

 placed in an incubator at 37 C. From time to time slides are removed from the solu- 

 tion, carefully washed in water, and in dilute acetic acid (0.1 per cent.) if the solution 

 used was alkaline, again washed in water, transferred to alcohol, stained in muchse- 

 matein, cleared and mounted in balsam. In this way the steps of the reaction, if any, 

 could be accurately followed. I found that the contents of the glands of Brunner 

 placed in a solution of barium hydroxide saturated at room temperature disappeared 

 in two hours ; that of the pyloric gland cells, of the gastric epithelial cells, and of the 

 goblet cells required ten to twenty-four hours for complete solution. The granules of 

 the Paneth cells were unaffected. The mucin from all the above cells was unaffected 

 by treatment with 5 per cent, solution of hydrochloric acid for twenty-four hours at 

 37 C. or by peptic digestion for the same length of time. The difference in the solu- 

 bility of the mucin from the several sources Brunner's cells, gastric epithelium, 

 goblet cells, etc. may be due to the unequal action of the fixing fluid (alcohol bichro- 

 mate sublimate), but, on the other hand, may indicate a chemical difference in the 

 nature of the mucins from these several sources. 



The cells of the pyloric glands in the opossum resemble the cells of the glands of 

 Brunner very closely. The differences which may be observed are of secondary 

 importance. The tubules of the pyloric glands and the cells composing them are dis- 

 tinctly smaller than those of the glands of Brunner. The internal structure of the 

 cells is, however, almost identical. The most obvious differences between the pyloric 

 glands and the glands of Brunner consist in the great number of cells of StOhr visible 

 in the former and in the greater ease with which the contained secretion may be stained 

 with muchsematein. The mucin of the pyloric glands may be stained by a weaker 

 solution of muchaematein, in which the glands of Brunner remain colorless. 



III. THE GLANDS OF BRUNNER OP THE CARNIVORA 



Next to the opossum in order of simplicity, as regards the structure of the glands 

 of Brunner and their relation to the pyloric glands, come the genera of the placental 

 orders, Carnivora and Insectivora. The structure and extent of the glands of Brunuer 

 in the cat and dog have been the subjects of numerous researches and are well known. 

 The facts as they present themselves in these animals are the foundations for most of 

 our knowledge, both physiological and histological, concerning the glands of 

 Brunner. 



From the standpoint of specialization, the glands of Brunuer of the cat and dog 

 present an advance on the condition fouud in the opossum, inasmuch as the ducts, 



292 



