SECRETION. 261 



no openings exist ; that the capillary blood-vessels, which form a 

 network upon the inner surface of the secretory canals, do 

 not secrete, but continue perfect canals till they become veins ; 

 and that the membrane itself, imbibing the blood and changing 

 its fluid portions, pours this forth from its own substance 

 upon its surface, and the secretion is performed not only at the 

 extremities of the canal, but throughout it. 



I agree, however, with those who believe that the new fluid 

 is not formed by the substance of the walls of the canals, but 

 passes formed from the minute twigs of the blood-vessels upon 

 its surface; and I think, with Blumenbach, that the infinitely 

 minute spaces, through which the fluid oozes into the secreting 

 canals, must be regarded as living, not inorganic, pores. For, 

 as I have already stated (p. 133.), the imbibition observable 

 after death is not found to occur during life. In the next place, 

 a secretion is not only increased by supplying the blood with 

 more of the materials furnishing it, and vitiated by vitiating the 

 blood, but may be rapidly and greatly augmented or altered 

 without any augmentation or alteration of the materials in the 

 vessels, merely by the administration of particular stimuli in 

 minute quantity, or by emotions of the mind. Healthy secre- 

 tion must be a living process, performed by living solids, and 

 the minute spaces through which this secreted fluid moves, are 

 spaces bounded by living solids, are apertures in living solids, 

 and therefore not inorganic pores. Indeed, although it has been 

 proved that glands are ducts beginning by blind extremities, 

 and not prolonged from blood-vessels, and have their blood- 

 vessels ramifying on their inner surface, I am not satisfied of the 

 existence of proof that these blood-vessels transmit their fluid 

 into the canal through apertures in their sides, and not by infi- 

 nitely minute twigs with open mouths. As absorption takes place 

 by the open mouths of vessels, secretion probably does the same. 

 But whether these are mere apertures, or from these apertures the 

 vessel is a little prolonged in the form of a minute twig, still the 

 openings are in living solids, and therefore must be subject, like 

 all the visible openings in the body, to the laws of life. If it is the 



P. Lupi, Nova per poros inorganicos secretionum theoria refutata, fyc. Romae, 

 1793. 2 vols. 8vo. 



Kreysig, Specimen Secundum ,- formerly recommended. 



Also C. Le Gallois, Le sang est-il identique dans tons les vaisseaux qu? ilparcourt ? 

 Paris, 1802. 8vo." 



