112 ZOOLOGY 



a critical demonstration of the relation of the individual secretory 

 granules to the detailed structural features of the Golgi apparatus." 

 (The term secretion is in all cases used to refer to the production 

 of a granule within the cell ; excretion refers to the act of extrusion 

 from the cell.) 



He describes the secretory cycle in a large number of glandular 

 tissues, such as salivary glands — parotid and submaxillary glands 

 of the cat, salivary glands of Limax ; pancreas — in salamanders 

 and cat ; liver — cat. All these are glands of the alimentary canal 

 and produce secretory granules of either the mucous or serous 

 type (Fig. 57). In both types of cells the Golgi apparatus, 

 which is in the form of a network, undergoes very considerable 

 hypertrophy at the onset of the secretory cycle. At that point, 

 however, the two types of cell cease to agree. The mucous secre- 

 tory granules grow fairly rapidly after their appearance and soon 

 reach their maximum size (Fig. 57, C). They are then pushed 

 outwards towards the lumen away from the Golgi network, which 

 remains more or less compact near the nucleus (between it and the 

 lumen). Fresh granules then make their appearance amongst the 

 network until the whole cell is packed with mucous granules 

 (Fig. 57, D). 



The serous cells show a different and more significant cycle. The 

 granules do not appear to attain their full growth at once, but the 

 Golgi network, which is greatly hypertrophied, extends through- 

 out the mass of granules and remains in intimate contact with 

 them until they are full-grown (Fig. 57, F-H). The granules all 

 appear to reach their full size at about the same time. 



In the case of Limax the Golgi apparatus is represented not by 

 a network, but by the scattered Golgi bodies characteristic of the 

 invertebrates. The same relationships exist here between the Golgi 

 bodies and the secretory granules as in the case of Golgi network. 



The importance of the different behaviour of the Golgi appa- 

 ratus in serous and mucous cells lies in the fact that it suggests 

 that the Golgi apparatus is definitely concerned in the process of 

 secretion. How else explain the different behaviour of the Golgi 

 than as an expression of physiological (chemical) differences in the 

 act of secreting different substances ? 



