92 PHYSIOLOGY CHAP. 



to the degree of digestive gastro-intestiual activity. According 

 to the observations of Heidenhain and his school, the secretion 



ceases in fasting dogs, and 



fcjgsse recommences during di- 



fcfjli 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 



$j&# seventh hours, after which 



it falls rapidly to the mini- 

 mum. The interpretation 



PIG. 29. Pancreas of dog with permanent fistula, 



showing changes in the alveolar cells owing to 01 tlllS Will be dlSCUSSed 



paralytic secretion. Alcohol - (carmine method. i i 



(Heidenhain.) elSeWllCie. 



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 transuclate. 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. K.J.T---> ^._, ^ ?sf : 



29). This change is an I #* e ^v tferj^S 



/ t>* ' ~"^"-. "</"* ' 



. n t "".._*> - . . 



exaggeration of what 3r.- . 



,1 i -1 /\- t- -. "y> ! :'" - '-"!.: '"'.- >- 



occurs in the gland m S^-% V^'^lfe^ 



normal digestion. fe'W %&^3 



According to Heideu- "^p-*^ 8 ^^ 



hain's histolosical studies r -!*v% ' 



- * "* '' ' ' ' 



of the pancreas, by the 



alcohol-haematoxylin and ^ ^'&* 



carmine method, in the ,^ ^^" ; 



first period of digestion 



(which extends to 6-10 



hours after the meal) the 



OUter, Staining ZOne OI Fj( ._ 30 __ Dn ,,, s pancreaSj 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). 



