THE MICROSCOPE. 155 



part; they are in the greatest abundance just in the upper part of 

 the mucous deposit. The crystals of oxalate of lime are very char- 

 acteristic and cannot be mistaken for anything else found in the 

 urine. It is to be borne in mind that some of these crystals are very 

 minute indeed, appearing only as angular points. This salt usually 

 crystallizes in well defined octahedra, but sometimes it is found in 

 the dumb-bell form. The dumb-bells of oxalate of lime are readily 

 told from those of uric acid both by microscopic and chemical 

 methods. The uric acid dumb-bell is dissolved at once in dilute 

 potash solutions while the oxalate of lime dumb-bell is insoluble even 

 in boiling potash solutions. Again, after the uric acid dumb-bell 

 has been dissolved by the potash, if an excess of acetic acid be 

 added the characteristic rhombic crystals will appear. 



Oxalate of lime is insoluble in water, alcohol, alkalies, and the 

 vegetable acids, hence it can be readily distinguished from the 

 phosphates which are soluble in acetic acid. 



This salt is soluble in the mineral acids and in the acid phos- 

 phate of soda. The octahedra of chloride of sodium can be distin- 

 guished easily from the oxalates by the fact that the former are 

 readily soluble in water, and that the urine must be evaporated to 

 show them. 



PEAR-GRIT. 



BY C. H. STOWELL. 



REFERRING to an article in the last number of this journal on 

 "Pear-grit as a Cause of Anal Irritation," Prof. S. Lockwood has 

 forwarded a copy of a paper he read before the New Jersey State 

 Microscopical Society in 1881, entitled "Faecal Sclerogen." He 

 diagnosed a case precisely as Dr. Rochrock did, and when the 

 patient ceased indulging in the popular Bartlett, all the disagreeable 

 symptoms at once subsided. The professor made a very nice test as 

 follows: During the summer flowers were very scarce, and his bees 

 were starving. Accordingly one day he supplied them with the 

 core and rind of a ripe Bartlett. The little workers literally cleaned 

 off to a nicety each individual granule, until specimens of sclerogen 

 were in abundance. This identified the faecal sand with the pear- 

 grit. The professor asks: "Why is the Bartlett so cathartic? May it 

 not be due to the mechanical action of this lignin grit?" 



