266 SECRETION. 



secretions, and the quality of the solids of the body, are affected 

 by the quality of the food and the absorption of different sub- 

 stances that alter the blood. Dr. Wollaston found the urine of 

 birds to be nearly pure uric acid, if animal food only was taken. 



If the kidneys refuse to secrete, urine may be found in the 

 ventricles of the brain ; and, when there was no outlet for it, an 

 urinous fluid has been furnished by the stomach, intestines, or 

 skin, &C. 1 In the latter cases, it may be said to have been fabri- 

 cated by the kidneys arid discharged by the other vessels, just 

 as the pus of an abscess has sometimes been absorbed and dis- 

 charged by the kidneys m : still we have the singular fact of vessels 

 allowing to stream through them a fluid totally different from that 

 which is natural to them. 



On the other hand, the circumstance of secretions being fre- 

 quently performed by vessels not destined or originally employed 

 for their production, though the blood remains the same, shows 

 how much depends upon the power of the part itself. Fat accu- 

 mulates in diseased ovaria, and even the fleshy substance of the 

 heart may be converted into it, as I once saw in a patient of my 

 own. Bone is every day deposited between the inner and middle 

 tunic of the arteries, and the serous membranes, or the subserous 

 cellular membrane, continually ossified. 



The bland mucus of the urethra may, by even mechanical irri- 

 tation of the canal, be converted to a foetid puriform fluid ; the 

 yellow bile and mild intestinal fluids to green, dark, scalding bile, 

 and foetid discharges, under the influence of acrid cathartics. 

 Different animals and different plants require different sorts of 

 food and soil, external supplies ; and produce different sub- 

 stances by nutrition and secretion under the same circumstances. n 

 So that the requisites for a given production are two materials 

 and organic powers ; and a change in either will occasion a change 

 in the product. 



1 See examples in Haller's El. Physiol. 1. vii. S. i. ix. Several such have 

 come to my own knowledge. Mr. Howship attended a lady who, he says, dis- 

 charged many quarts of urine alternately from the bladder and rectum, after 

 intervals of several weeks of suppression ; and this for four years without serious 

 injury. Practical Treatise on Diseases of the Urinary Organs. 1823. 



m See Dr. Hennen's Military Surgery ; and perhaps Heberden's Commentarii, 

 p. 408. 



n " If wheat and peas be sown in the same water, earth, or medium, the 

 former will uniformly deposit silex in their cuticle, and the latter none." Intro- 

 duction to Botany, by John Lindley, F. R.S. Prof, of Botany in the University 

 of London, p. 233. 



