DR DAVY ON THE URINARY SECRETION OF FISHES. 545 



by alcohol and nitric acid, indications were afforded of the presence also of a little 

 albumen and urea, but without any trace of lithic acid. 



Of the fishes before named, destitute of a urinary bladder, the ureter, in the 

 instance of the haddock {Morrhua ceglefinus), of the cod (Morrhua vulgaris), of 

 the pollack (Merlangus pollachius), of the turbot (Rhombus maximus), was found 

 so capacious, that it might answer the purpose of a receptacle or bladder. In 

 each its inner surface was wet ; but only in one, that of the turbot, was there any 

 fluid collected. The quantity obtained, by cutting out the duct, after a ligature 

 had been passed above and below, was about ten drops. It was colourless, not 

 quite clear, and had suspended in it a few white flakes. These were not dissolved 

 by nitric acid, nor did they, when the acid was evaporated by heat, afford any 

 the slightest indications of lithic acid. The residue was yellow ; nor could urea 

 be detected in the minute portion of fluid. 



Of the bream (Pagillus centrodontus), the ureter is narrow, and of little ca- 

 pacity ; as is also that of the conger (Conger vulgaris), and that of the mackerel 

 (Scomber scombrus). Of all three the ureter was found merely moist — wet — as if 

 a fluid had passed ; in neither could any solid matter be detected. At the ter- 

 mination of the ureter of the bream a minute portion of whitish matter was 

 seen adhering, suggesting lithate of soda or ammonia, but not confirmed when 

 tested ; for, when acted on by nitric acid and heat, the colour acquired was yel- 

 low, without the slightest tinge of purple. 



I may mention, generally, that in most of the fishes, the names of which have 

 been given, I did not omit examining the cloaca, but with results so unsatisfac- 

 tory, that they might be said to have been negative. Often there was an ap- 

 pearance as if of the presence of an alkaline lithate ; but, when tested, it was 

 found to be different, and the matter chiefly intestinal excrement. In the in- 

 stance of one only, and that a sea-trout (Salmo trutta), was a trace of urea indi- 

 cated, judging from the form of the minute microscopic crystals obtained on eva- 

 poration, after treatment with alcohol and nitric acid. 



I may also mention, generally, that in each fish I carefully inspected the struc- 

 ture of the kidneys ; but without success as to the finding of any matter conspi- 

 cuous to the eye, such as is commonly seen in the same organs in the instance of 

 serpents and lizards, viz., the opaque lithate. 



In one instance only, that of the haddock, have I examined these organs che- 

 mically. The result, too, was negative. The trial was made, first by digesting 

 the kidneys in alcohol, decanting the clear spirit, evaporating it at a low tempe- 

 rature, and to the concentrated extract obtained adding nitric acid ; secondly, 

 by digesting the organs with aqua ammonise, filtering the solution, and testing 

 the little extract obtained by nitric acid and heat. 



If any conclusions are permissible from the preceding few and imperfect ob- 

 servations, I would venture to submit the following: — 1st, that the urinary secre- 



