BLOOD. 185 



the cn-stalline form of the oxalate of urea when alcohol-extract 

 of urine, not very rich in urea, is treated with oxalic acid. In 

 a, we see the characteristic crystalline form of the oxalate of 

 urea ; b, represents various groups of it. If the alcohol-extract 

 of blood containing no m-ea be similarly treated, the crystals of 

 fig. 7 are produced. Lastly, fig. 8 shows the crystals of oxahc 

 acid itself, which are veiy similar to those of pure crystallized 

 urea. 



On treating the extractive matter of blood containing no 

 urea with nitric acid, I have occasionally perceived crystals 

 which, at first sight, appeared extremely similar to those of 

 nitrate of m'ea, but which were in reality composed^of nitrate 

 of soda. These crystals are exhibited in fig. 9. They possess 

 a very remarkable degree of thickness,^ which I have endea- 

 voured to represent in the plate. They may be distinguished 

 fi-om the similar form of nitrate of rn-ea, by the circumstance 

 that the former are not at all soluble in anhydrous alcohol, while 

 the latter are readily dissolved in it. If nitrate of m-ea be pre- 

 sent, it will recrystalhze from its alcoholic solution in groups 

 similar to those in fig. 10. 



2. Sugar. This substance, which I once discovered in the 

 blood of a calf, is very seldom to be found in healthy blood, 

 although in certain pathological states, especially in diabetes 

 meUitus, it has frequently been detected. If the quantity be 

 very small, its presence is not always easily recognized. It is 

 found mixed with the extractive matters, if the blood is analysed 

 according to my directions, and if it exists in any quantitj^, 

 may be recognized by the taste. If only a very little sugar be 

 present, it is adrisable to precipitate the protein-compounds 

 from a large quantity of blood, with spirit. The fluid must 

 then be filtered and evaporated to a small residue, Avhich must 

 be treated with anhydrous alcohol. The sugar, if present, must 

 be taken up by the alcohol. If, after due evaporation, the 

 residue have a sweetish taste, a portion of the sugar may be 

 obtained tolerably piu-e, since its quantity cannot be very incon- 

 siderable. "With this riew we dissolve it in a Uttle water, add 

 alcohol of -833, and allow it to stand for some time ; under 



' This is easily seea by slightly varying the fcciis. 



