THE FUNCTIONS OF THE DIGESTIVE ORGANS. 487 



been found that if a mercury manometer be introduced into the exit duct, 

 then after stimulating the cerebral secretory nerves, the mercury will in a 

 short time rise 100 millimeters or more higher in this manometer than in 

 another one that is placed in the carotid artery. There is, therefore, a 

 considerable increase of pressure during the secretion of saliva. 1 It is also 

 an important fact that stimulation of the secretory nerves has an effect 

 even in animals from which the blood has been removed completely. 

 That the cells of the gland are active during the preparation of saliva, is 

 evident from a microscopic examination during a period of rest and one 

 of action. 2 We have to thank Heidenhain 3 for this interesting information. 

 He described the contents of the albuminous glands at rest and after 

 secretion had taken place, using alcoholic-carmine preparations. In the 

 first instance, a shrunken, finely granular substance is seen in a clear, 

 uncolored background. The nucleus itself appears as an irregular, serrated 

 structure without any distinct nucleolus. On making preparations in the 

 same way of glands which have been in marked activity for some 

 time, under nervous stimulation, there is a quite different appear- 

 ance. The size of the cells has increased to a greater or less extent. The 

 nucleus no longer appears serrated, but round. The nucleolus is now 

 much more sharply outlined, and there is a considerable increase in the 

 amount of substance in the vicinity of the nucleus so that the cells appear 

 opaque. The glands themselves show similar changes. During a period 

 of rest its gland-cells are large and clear. Their nuclei are flattened and 

 parietal. The protoplasm is small in amount. The chief constituent 

 in the composition of the cells is a clear substance which represents the 

 secretion material of the gland-cells. When the gland becomes active the 

 nuclei become round. The nucleoli become more distinct, and at the same 

 time the nuclei are pressed more and more to the center of the cells. The 

 cells themselves become smaller on account of loss of the above-mentioned 

 clear substance. At the same time, there is an increase in the amount 

 of protoplasm, evidently the beginning of the production of a new secretion. 

 If we examine fresh material, instead of hardened preparations, we will 



1 We might mention in this connection the formation of retention cysts which often 

 take place in the parotid gland when the duct from a lobule becomes stopped up for 

 any reason ; for example, in case of inflammation. If the secretion of saliva were to be 

 regarded as a mere filtration process, it would be expected that the activity in the region 

 cut off would soon cease. The secretion, however, continues. The amount of pressure 

 developed in consequence is indicated by the swelling produced. Even if, later on, 

 secondary changes appear, creating new conditions, still for the beginning of the forma- 

 tion of cysts our observation holds true. 



2 Cf. A. Noll: Die Sekretion der Driisenzelle, Ergeb. Physiol. (Asher and Spiro) Jg. 

 IV. p. 84 (1905). 



3 Zentr. med. Wissensch. 9, 130 (1866). Hermann's Handbuch der Physiol. 5, L 

 64 (1883). 



