INOKGANIC CONSTITUENTS OF URINE. 



695 



times they are six-sided, resembling crystals of cystine, but dis- 

 tinguishable from the latter, by two of their sides being longer 

 than the others. Occasionally they appear as truncated or 

 rounded columns. 



Cystine crystallizes in flat, hexagonal plates, with irregularly 

 hexagonal markings on their surface. Sometimes radiating 

 lines pass from an opaque centre to the margins. (Fig. 416.) A 

 deposit of cystine may be readily distinguished from that of 

 the pale urates, which it resembles in appearance, by not dis- 

 solving when heated. 



Oxalate of Lime occurs in oc- Fio. 4i7. 



tohedral crystals, having one 

 axis shorter than the other two. 

 It is important to remember 

 that these crystals difler in ap- 

 pearance, according to the j^osi- 

 tion in which they are viewed, as 

 shown in Figs. 417, 418. When 

 large they may be seen with the 



Fio. 418. 



Various forms of oxalate of lime. 



unassisted eye as minute glistening points imbedded in the sedi- 

 ment. "Where crystals of the oxalate of lime are associated with 

 and obscured by the pale lithates, the addition of a drop or two 

 of solution of potash, by dissolving the latter, will render the 

 former more apparent. 



Occasionally oxalate' of lime assumes the form Fio. 4i9. 



of dumb-bells. Dr. Golding Bird considers these ^ ^ 

 to consist of oxalurate of lime, on account of Ip ^^ ^^ 

 their polarizing influence upon light. (Fig. 419.) 

 The dumb-bell crystals are probably compound, 

 appearing to be formed of collections of minute 

 acicular crystals. They are generally accom- ^ '^ 



panied by tlie octohedral form, and, according to Dumb-beii crystals. 

 Dr. Beale, their appearance is sometimes pre- 

 ceded and succeeded by the presence of the circular, oval, and 

 less regular forms of crystals. They are formed in the kidney, 



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