92 



PHYSIOLOGY 



CHAP. 



BF^aj 



fe> 



to the degree of digestive gastro-intestinal activity. According 

 to the observations of Heidenhain and his school, the secretion 



ceases in fasting dogs, and 



~A.^,2^fe:.r^J^fe:V^9fiAlM^> recommences during di- 

 gestion, continuing with 

 fairly regular fluctuations 

 throughout the process. 

 The rate of secretion 



reaches its height in the 

 first 3 hours of digestion, 

 then slowly diminishes, to 

 rise again to a second maxi- 

 mum between the third and 

 seventh hours, after which 

 it falls rapidly to the mini- 

 mum. The interpretation 



FIG. 20. Pancreas of dog with permanent fistula, , . . . . , \. 



showing changes in the alveolar cells owing to Ot thlS Will DC dlSCUSSCd 



paralytic secretion. Alcohol - carmine method. .-.1 .,, T ,V 1C>T , 



(Heidenhain.) ei&ew^nere. 



In dogs, too, pancreatic 



secretion may become continuous if the state of the gland is 

 altered. In this case (which recalls the paralytic secretion of the 

 salivary glands) the juice secreted is fluid and highly similar to 

 an ordinary transudate. The alveoli of the gland are reduced ; 

 the secretory cells have 

 lost the inner zone and 

 only keep the outer, so 

 that their whole contents 

 stain with carmine (Fig. 

 29). This change is an 

 exaggeration of what 

 occurs in the gland in 

 normal digestion. 



According to Heiden- 

 hain's histological studies 

 of the pancreas, by the 

 alcohol-haernatoxylin and 

 carmine method, in the 

 first period of digestion 

 (which extends to 6-10 

 hours after the meal) the 

 outer, staining zone of T 



. . FIG. 30. Dogs pancreas, excised during first period of 



Secretory Cells IS enlarged digestion. Alcohol-carmine method. (Heideuhain.) 



in dogs; the inner, granular 



zone almost entirely disappears, so that the glandular alveoli 

 seem as a whole to be diminished in diameter. The alveoli 

 never show uniform changes, some being more, others less, 

 modified by the secretory process (Fig. 30). 



