196 JOHN SUNDWALL 



in cell types 2 and 3 it is round or oval and separated from the 

 base of the cell by a narrow zone of cytoplasm. However, no 

 distinct changes are seen in the chromatin. In both instances 

 one or frequently two large chromatin masses are surrounded by 

 numerous finer granules of chromatin. The change of position 

 and form of the nucleus may be due entirely to the quantity of 

 granules. The nucleus of the intercalary duct, on the other hand, 

 shows no appreciable change in form or position whether the 

 cell is at its maximum stage of granule formation or its minimum. 



The fixation and staining of granules. When the tissues are 

 properly fixed in either Bensley's solution or formalin bichloride 

 bichromate solution all granules are conserved. Such is not 

 the case when alcohol, Zenker's or numerous other fixatives are 

 used. Zenker's and Altmann's fix the granules in the intercalary 

 duct and frequently in some few cells in the tubules. The 

 granules in the large bulging cells are not preserved in alcohol, 

 Altmann's, or Zenker's but, instead, the intergranular network 

 remains. 



Neutral gentian, safranin acid violet, copper chrome haemato- 

 xylin, iron haematoxylin, muchaematein, and mucicarmin 

 proved to be the most satisfactory stains for the granules. 



Are secretory cells of tubules similar in function? Notwith- 

 standing the variable staining reactions on the part of granules 

 and the various sizes and shapes of cells, cells of the tubules 

 are doubtless similar in function. We have no evidence that 

 more than one functional type of cell is present. Proof of this 

 is seen in the granular stage when all the cells of the tubules 

 stain similarly. Furthermore other structures in these cells 

 are alike so far as I have been able to make out. The changes 

 in position and form of the nuclei only represent different secre- 

 tory phases. 



Staining reaction of granules, selective action. In order to 

 prove that the cells in both the tubules and the intercalary 

 ducts are capable of taking various granular stains, serial sec- 

 tions three micra thick were cut and fastened to different slides — 

 one section for each slide. The first section was stained with 

 neutral gentian, the second with muchaematein, the third with 



