THE MICROSCOPE. 69 



In the alkaline phosphates we have phosphorus combined with 

 sodium and potassium. This combination exists in the blood as well 

 as in the urine ; being very soluble they are never found as a deposit 

 in the urine. 



In the earthy phosphates calcium and magnesium enter into 

 combination with the phosphorus. They are held in solution by the 

 acidity of the urine, when this acidity is lost, the result of disease, 

 application of heat, or saturating, a deposit is thrown down called 

 the amorphorus phosphates of lime and magnesia. They may be 

 mistaken for urates under the microscope but easily distinguished by 

 chemical tests. They are soluble in acids, insoluble in alkalies, and 

 do not disappear by heating, while on the contrary the urates will 

 disappear by the application of heat, are soluble in alkalies and 

 insoluble in acids. 



One of the most important of the urinary deposits is the pris- 

 matic or triple phosphates, a variety of the ammoaio-magnesian phos- 

 phates. 



This is one of the characteristic crystals of alkaline urine ; they 

 are the result of the slow decomposition of the urea into ammonium 

 carbonate, the urine is alkaline in reaction, and acquires a strong 

 ammoniacal odor. When this change takes place, either within or 

 without the body, we have as a result the triple phosphates, the 

 ammonium combining with the magnesium and phosphoric acid, 

 forming in beautiful transparent prismatic crystals with obliquely 

 truncated or beveled ends nicely illustrated in fig. 3. When once 

 seen under the microscope by a careful observer they need never be 

 mistaken for any other urinary deposit. At times some of these 

 crystals appear almost square, resembling the octahedra oxalates of 

 lime, and may at a glance be mistaken for them, but chemical tests 

 will soon decide. 



These crystals are said to have been found in acid urine, but 

 there is a difference of opinion among chemists regarding it. Beale 

 says, "the acid reaction may be due to some salt present that red- 

 dens litmus paper and not to a free acid." 



Unless these crystals are persistent in the urine the condition 

 need not necessarily b^ pathological, but if continued, demands the 

 attention of the physician and calls for repeated microscopical 

 examinations of the urine. 



The microscope will usually reveal, associated with these pris- 



