'I'llK LACHin MAI. Cl.ANl) 



215 



intracellular although it is impossible to demonstrate by this 

 methotl that such is the case. 



The lumina of the intercalary ducts appear either smooth and 

 even or man}' short knot-like projections are seen on either side 

 showing that the surface cells which foi'm the lumina are either 

 in close apposition to each other or have indentations between 

 them. That both conditions may be present has been considered 

 in "Duct Svstem and Tubules." 



Fig. 17 Tuhule and iuterrahiry duct after vital .staining with pyronin. 

 Toch. \'r. 1. .-I, secretion capillaries; 7?, liimon of tnliule: C, lumen of intercalary 



Pjironin 



The most satisfactory method for the study of secretion 

 capillaries is the vital staining with pyronin. The capillaries 

 as well as the lumina of the tubules and ducts stain a deep red 

 while the cells are unstained (fig. 17). The advantage of this 

 method lies in the fact that very thin sections from 2 to 5^ can 

 be obtained and these can be further stained with either iron 

 haematoxylin or copper chrome haematoxylin. Thereby the re- 

 lation of the capillaries to the other structures of the cells can 

 be readilv made out. 



