CONCERNING THE SECRETION OF FERMENTS BY THE LIVER CELLS 453 



this point further investigation is necessary and is now being carried out in 

 my laboratory. Possibly psychic sécrétion may also be due to » secretin « . 



4. The amount of the second sécrétion and the time required to 

 recover from it dépend entirely upon the nature of the food; secretory 

 activity is intense and prolonged with diets containing abundance of proteid 

 material, but scanty and of short duration when carbohydrates and fats are 

 administered. We may conclude, therefore, that the liver, like the stomach 

 and pancréas, works to a nicety, only producing the exact amount of 

 digestive ferments required to deal with the kind of food ingested and no 

 more. This seems to be an absolute law of ferment production by the 

 organism, necessitated by the exhaustive process required for the manu- 

 facture of such bodies by living animais. 



5. Another very interesting point is the fact established by this 

 research that the liver cells work as producers of ferments in relays. 

 Zymogen production is initiated in ail cases by the small cells bordering on 

 the portai tracts, it extends to the outer zone of the lobules and thence to 

 the middle and inner zones, the cells surrounding the intra-lobular veins 

 being the last to part with their store of ferment; recovery after exertion 

 follows the same course, the small cells being the first and the cells round 

 the hepatic vessels being the last to completely regain the characteristic 

 appearances observed in resting cells. 



6. The vacuolation, often excessive, that occurs in the liver cells im- 

 mediately after recovery from psychic sécrétion is very interesting; it is 

 especially marked with fat and mixed diet containing fat; with other foods 

 the vacuoles are very small or absent altogether, therefore it has probably 

 some relation to the ingestion of fat, but what its précise significance may 

 be cannot at présent be determined. 



Vacuolation, which is always présent at a later stage, is chiefly due to 

 the présence of glycogen in the cells, as can be demonstrated by the usual 

 methods adopted for the récognition of that substance. 



7. The precipitate produced in the cytoplasm by the fixing reagents 

 used in thèse experiments varies somewhat in appearance and in staining 

 properties with the nature of the food. 



The spherules so produced are largest when repair is in active progress 

 and may be taken as an indication of the amount of material taken up by 

 the cells from the blood, but beyond this, the indications furnished by the 

 préparations are scarcely adéquate to serve as a basis for any definite 



