402 PHYSIOLOGICAL CUEMISTRT. 



spectroscope, the guaiacum test, and HELLER'S or HELLER- 

 TEICHMANN'S test. 



Microscopic Investigation. The blood-corpuscles may remain 

 undissolved for a long time in acid urine ; in alkaline urine, on the 

 contrary, they are easily changed and dissolved. They often 

 appear entirely unchanged in the sediment ; in some cases they are 

 distended, and in others unequally pointed or jagged like a thorn- 

 apple. In hemorrhage of the kidneys a cylindrical clot is some- 

 times found in the sediment which is covered with numerous red 

 blood-corpuscles, forming casts of the urinary passages. These 

 formations are called BLOOD-CYLINDERS. 



The spectroscopic investigation is naturally of very great value; 

 and if it be necessary to determine not only the presence but also 

 the kind of coloring matter, this method is indispensable. In 

 regard to the optical behavior of the various blood-coloring matters 

 we must refer to Chapter IV. 



ALMEN'S Guaiacum Test. Mix in a test-tube equal volumes of 

 tincture of guaiacum and old turpentine which has become strongly 

 ozonized by the action of air under the influence of light. To this 

 mixture, which must not have the slightest blue color, add the urine 

 to be tested. In the presence of blood or blood-coloring matters, 

 first a bluish-green and then a beautiful blue ring appears where 

 the two liquids meet. On shaking the mixture it becomes more or 

 less blue. Normal urine or one containing albumin does not give 

 this reaction. For the reason of this we must refer the reader to 

 Chapter IV, page 71. Urine containing pus, although no blood is 

 present, gives a blue color with these reagents ; but in this case the 

 tincture of guaiacum alone, without turpentine, is colored blue by 

 the urine (VITALLI). This is at least true for a tincture that has 

 been exposed for some time to the action of air and sunlight. 

 The blue color produced by pus differs from that produced by 

 blood -coloring matters by disappearing on heating the urine to 

 boiling. A urine alkaline by decomposition must first be made 

 faintly acid before performing the reaction. The turpentine should 

 be kept exposed to sunlight, while the tincture of guaiacum must be 

 kept in a dark glass bottle. These reagents to be of use must be 

 controlled by a liquid containing blood. This test, it is true, in 

 positive results is not absolutely decisive, because other bodies may 



