200 THE SECRETIONS: 



36 b.) This is best observed under a half-inch object-glass ; as 

 with a higher power this appearance is lost. 



In a very few cases the oxalate is met with in very remarkable 

 crystals, shaped like dumb-bells, or rather like two kidneys with 

 their concavities opposed, and sometimes so closely approxi- 

 mating as to appear circular, the surfaces being finely striated. 

 (Fig. 36 c.) 



The greatest possible variation in the size of these crystals 

 is met with not only in different specimens of urine, but often 

 in the very same portion. In a single drop of urine octohedra 

 of oxalate of lime may be frequently observed mixed with others 

 four or six times their size. Dr. Golding Bird has given the 

 following measurements of some of his preserved specimens : 



inch. 



Length of a side of the largest octohedra . . '730 



smallest ditto . . . 5^5 



Long diameter of large " dumb-bell" crystals . . 5 g g 



Short diameter of ditto . -jso 



Long diameter of the smallest " dumb-bells" . . -j^ 



Short diameter of ditto .... %sm 



In the urine of the horse they are much larger, often being 

 1-1 50th of an inch long. 



Many specimens of oxalic urine give a precipitate with salts 

 of lime, insoluble in acetic acid, and consisting of oxalate of 

 lime. This is often dependent on the presence of oxalate of 

 ammonia, and delicate acicular crystals of this salt may be occa- 

 sionally noticed, during spontaneous evaporation, on the border 

 of the capsule. 



Lehmann states that he has very frequently met with oxa- 

 late of lime in healthy urine, and that it often occurs in 

 large quantity in cases of tuberculosis, arthritis, and especially 

 of osteomalacia or softening of the bones. He has likewise 

 met with it in endocarditis and other acute diseases. He 

 states that the crystals are neither octohedra nor cubes, but 

 four-sided double pyramids, which in their projection under 

 the microscope appear as very minute cubes, or as somewhat 

 larger octohedra. He further believes that a portion of the oxa- 

 late of lime is held in solution by lactic acid, and advises that 

 if the urine be very acid, it should be neutralized, boiled, and 

 allowed to cool slowly, before looking for the crystals. 



