SECRETION. 265 



fluids appear produced in small quantity from a given surface ; 

 and a fluid nearly aqueous, or at least with no peculiar consti- 

 tuent, is produced from so small a surface as that of a mucous or 

 serous membrane, or crypts or follicles. Whatever may be 

 the constituents of the fluid, if they are secreted with a large 

 quantity of water, the complexity and bulk are not in proportion 

 to the quantity of such secretion. For instance, the urine far 

 exceeds the bile in quantity, yet the two kidneys together are 

 not more conglomerated, and are smaller, than the liver ; for the 

 elaborate contents of the urine are greatly diluted with a fluid 

 which requires no extent of surface for its production. I should, 

 perhaps, say that the elaborate nature of a secretion, its amount, 

 and its concentration, are all elements that require a more ex- 

 tensive secreting surface; and this is given by both complication 

 and amount of canals, so that the relations of a secretion and 

 the secreting organs depend not on one, but the whole, of these 

 points. As a connection of peculiarity of secretion with pecu- 

 liarity of structure cannot be discovered, the cause of such 

 secretion must be certain unknown powers of the secreting 

 organs, as inexplicable as the powers of formation and the 

 powers of nutrition. 



It is of no consequence, in the case at least of some organs, by 

 what vessel the blood is conveyed to the secretory apparatus. 

 Mr. Hodgson, on opening the body of a diabetic person, found 

 the cavity of one renal artery obliterated by an accumulation of 

 atheromatous and calcareous matter in its coats. The glandular 

 structure was perfectly natural. The pelvis contained urine, and 

 a considerable quantity of that fluid was found in the bladder. 

 The kidney was supplied with blood by a large branch from one 

 of the lumbar arteries and by the arteries of the renal capsule. 1 

 Dr. Andral once found a kidney in the pelvis, and supplied by the 

 hypogastric artery . k When a breast which secreted good milk is 

 situated on the thigh, we have another illustration of the same 

 fact. 



The quality of the blood, however, from which the part has to 

 fabricate the new substance is important. The liver is supplied 

 with venous blood as the material, and so are the kidneys of am- 

 phibia. We cannot suppose that arterial blood would have been 

 suitable. For other secretions dark blood is unsuitable. Various 



1 A Treatise on the Diseases of Arteries and Veins, $c. 

 k Precis tfAnat. Pathol. t. ii. P. ii. p. 628. 



