infrastructure of Glands 25 



when the pH of the medium exceeded 6-8. Hokin suggested that 

 dissolution of the granules occurred after ejection into the alkaline 

 pancreatic juice, but the observations of Siekevitz and Palade 

 (1958) do not support this. 



The Golgi apparatus known from supravital staining in the light 

 microscope has turned out to have a well-defined although enig- 

 matic appearance in the electron microscope. It consists of one or 

 a series of vacuoles with concentrically arranged membranes 

 embedded in the perinuclear ground substance (Sjostrand and 

 Hanzon, 19546; Dalton and Felix, 1956; Lacy and Challice, 1957) 

 giving a quite characteristic appearance. The neutral red bodies 

 studied extensively by Hirsch (1932) and others are not in the true 

 Golgi apparatus, but are artefacts due to the cytotoxic action of 

 this substance (Weiss, 1955). 



Sjostrand and Hanzon (19546) found all stages of evolution of 

 zymogen granules apparently occurring in relationship to the 

 Golgi apparatus of pancreatic acinar cells. This supports the many 

 observations made with the light microscope suggesting a relation- 

 ship between the Golgi system and secretory granules (see Jun- 

 queira and Hirsch, 1956). There was no apparent connection 

 between the Golgi system and the mitochondria, but presumably 

 the Golgi system is continuous with the e.r. The Golgi apparatus 

 in salivary cells is very similar to that found in other secreting cells 

 (Leeson and Jacoby, 19596). Schneider and KufT (1954) have 

 isolated a highly purified suspension of the Golgi system from 

 homogenates of epididymis and found a very high content of lipid 

 phosphorus (200 jug/mg N) and a high content of RNA and alka- 

 line phosphatase, but other enzyme activities tested were low and, 

 in particular, there was no detectable cytochrome oxidase or 

 desoxyribonuclease. 



The nucleus in secreting cells does not have any specific features, 

 but appears as a rather uniform granular sphere surrounded by a 

 coarsely pored double membrane. 



Scott and Pease (1957) identified nerve fibres penetrating the 

 basement membrane of salivary acini and ending as fine filaments 

 directly applied to the basal and intercellular surfaces of the acinar 

 cells. No nerve fibres were seen ending on duct cells. 



Myoepithelial cells in the electron microscope (Fig. 2.10) 

 resemble quite closely smooth muscle ; this may be taken to sup- 

 port the theory that they are contractile in function. 



