1879.] 



Serous Glands in Rest and Activity. 



379 



rabbit has parotid alveoli throughout granular, the secretion is not 

 solely dependent on feeding, but in whatever stage the glands are at 

 the beginning of an experiment, they become less granular after 

 having been made to secrete. 



I have said that the changes can be seen either after sympathetic 

 stimulation or after injection of pilocarpin. This is noteworthy, since 

 Heidenhain,* dealing with alcohol-hardened specimens, failed to 

 observe any of the changes after pilocarpin injection, which he could 

 obtain by stimulation of the sympathetic nerve. 



The appearances in the gland described above are not observed in 

 alcohol- hardened specimens. 



It will be remembered that Heidenhain describes the secreting 

 gland as being, in alcohol specimens, more granular than the resting ; 

 this depends on the relative amounts of cell substances soluble and 

 insoluble in alcohol. 



Treated with osmic acid and subsequently with alcohol the gland 

 has a markedly different appearance in the resting and active state. 



In the resting state the alveolar cells viewed with a Zeiss F have 

 a close-meshed network throughout. The nuclei are fairly apparent, 

 evenly stained, rather compressed, and peripherally placed. With 

 Zeiss D the cells appear densely granular. 



In the active state the punctated look caused by a network and in- 

 terfibrillar substance of differing staining power is absent, the cells 

 stain fairly evenly throughout, thus the nuclei are with difficulty seen ; 

 they are spherical, and are placed more in the middle of the cell. 



The Parotid Gland in the Dog, Cat, and Bat. 



In these animal? the account given above of the resting and active 

 states in the main holds. A more prolonged secreting activity is, 

 however, necessary to produce the clear zone and star arrangement of 

 the granules. 



In a former paper f I have mentioned that when just sufficient 

 atropin to paralyse the secretory nerves is injected into the blood, the 

 paralysing effect can be antagonised and a slight secretion obtained 

 many times in succession "by injecting small quantities of warm pilo- 

 carpin into the duct. I was curious to observe if the secretion 

 obtained by repeatedly antagonising the atropin effect would produce 

 the secretory change. The experiment was tried on a cat, and with a 

 positive result, the granules at the periphery of the alveoli disappeared, 

 a clear zone was formed. 



In the dog few observers have seen any saliva follow stimulation of 

 the sympathetic nerve. Heidenhain £ obtained only now and then a 



* PfMger. "Arch. f. cl. Gres. Physiologie," Bd. xvii, p. 45, 1878. 

 f Foster. " Journal of Physiology," vol. i, p. 356, 1878. 

 % Op. cit., p. 29. 



2 n 2 



