328 



Prof. F. Smith. 



[June 20, 



from any change of hahit on the part of the Fish, ceased to exist ; and 

 hence the widespread degeneracy of that organ. 



(III.) In all the Siluridse normales the air-bladder is a rudimentary 

 and more or less fnnctionless structure, and the numerous modifica- 

 tions which it presents in this group afford abundant illustrations of 

 the extreme variability to which all degenerate organs are liable. 



(IV.) As far as the evidence at our command will enable us to 

 generalise, it seems extremely probable that the degeneracy of 

 the air-bladder in the S. normales is due to their assumption of a 

 ground habit, whereby the continued existence of an air-bladder, 

 capable of functioning as a hydrostatic apparatus, is rendered 

 unnecessary. 



(V.) That inasmuch as the assumption of a ground habit is almost 

 invariably attended by degeneration of the air-bladder, which must 

 have the effect of rendering the Weberian apparatus inoperative, it 

 seems to us a reasonable inference that the mechanism in question is 

 related neither to the function of audition as Weber contended, nor 

 to the appreciation of varying atmospheric pressures, as suggested by 

 Sagemehl, but rather to the perception of the varying hydrostatic 

 pressures to which the Fish is continually exposed. (Hasse's theory). 



(VI.) Certain facts appear to throw some light on the nature of 

 the Weberian ossicles. The discovery of ascending processes to the 

 intercalaria, which form part of the wall of the neural canal, and are 

 interposed between the foramina for the exit of the second and third 

 special nerves, is confirmatory of the view, first suggested by Baudelot 

 and supported by Ramsay Wright, that the ossicles in question 

 represent the metamorphosed neural arch of the second vertebra. 

 The mode of origin of the tripodes in Auchejiipterus, if not due to 

 secondary fusion with the arch of the complex vertebra, but to the 

 retention of a primitive continuity, is also confirmatory of the views 

 of the same morphologists, that those ossicles represent the transverse 

 processes of the third vertebra. 



VIII. " The Chemistry of the Urine of the Horse." By Fred 

 Smith, M.R.C.V.S., F.I.C., Army Veterinary DepaVtment, 

 Professor, Army Veterinary School, Aldershot. Comnmni- 

 cated by Sir William Aitken, F.R.S. Received June 20, 

 1889. 



I have attempted in the following paper to record the results 

 obtained from a series of analyses of the urine of the horse in health. 

 When I first commenced my subject I was under the impression 



