ROBERT RUSSELL BENSLEY 23 



lumen 16 p to 20 p in width. The clear cells of the glands of Brunner of the rabbit 

 are mucous cells, very similar in type to those of the animals already described. A 

 number of tubules formed by cells of this type is represented in Plate XXI, Fig. 5. 

 The body of the cell presents a coarsely reticular structure, the meshes of which are 

 filled with the reserve secretion of the cell. This secretion may be stained by the use 

 of the stronger muchEematein, or of mucicarmine, or of Mann's methyl blue-eosin in 

 which it stains blue, or of the eosin-aurantia-indulin mixture recommended by the 

 writer for staining the secretion of the pyloric glands. The appearance of the secre- 

 tion when so stained differs according to the mode of fixation and subsequent treatment 

 of the tissue. In material fixed in aqueous solutions of corrosive sublimate, the secre- 

 tion presents the reticular appearance characteristic of mucous cells. The same remark 

 is true of material fixed, without previous removal of the tunica muscularis, in the 

 alcoholic sublimate-bichromate mixture. If, however, the muscular coat of the intestine 

 is removed, and the organ then fixed in the last-mentioned mixture, so as to permit the 

 sublimate and bichromate to come at once into contact with the cells, the secretion is 

 found to be in the form of distinct granules which are, when so fixed, more resistant to 

 the action of water and therefore more permanent in preparations than the correspond- 

 ing structures in the cells of the opossum. According to the phase of functional 

 activity the secretion is subdivided more or less completely into proximal and distal 

 masses. In Fig. 5, which represents the fully loaded condition, traces of the transverse 

 band of cytoplasm separating the two masses are still visible in most of the cells. The 

 basal cytoplasm is small in amount and contains no basal filaments. 



Sections of the fresh tubule examined in blood serum or in salt solution appear 

 perfectly transparent, the granules of secretion corresponding so closely in refractive 

 index to the surrounding medium that they remain invisible. 



In material fixed in absolute alcohol and tested by Macallum's microchemical 

 method for the detection of organic compounds of iron, a very faint positive reaction is 

 obtained in the cytoplasm around the nucleus. By Macallum's modification of Lilien- 

 feld and Monti's method for the microchemical detection of phosphorus, the cytoplasm 

 gives a reaction no stronger than that obtained in the cytoplasm of the cylindrical cells 

 of the surface epithelium. The secretion masses remain colorless in this test. 



Both in the fresh tissue and in stained sections, the dark tubules present appear- 

 ances totally different from those just described. In the fresh material examined in 

 blood serum the dark tubules exhibit two well-marked zones. The outer zone is 

 perfectly clear and transparent, no structures whatever being visible in it. The inner 

 zone, on the contrary, is occupied by large numbers of closely packed, minute, highly 

 refractive granules. The appearance of such a fresh tubule is shown in Plate XXI, 

 Fig. 7. The resemblance to a fresh pancreatic tubule or to an active acinus of a 

 serous gland is striking. 



In the stained preparations these tubules are distinguished from the mucous 

 tubules by their remarkable staining capacity. The lumen is so small as to be scarcely 



299 



