APPENDIX 491 



extract residue with six times its bulk of methylated spirit, evaporate 

 this extract to dry ness, dissolve residue in 3-4 c.c. distilled water, and 

 add to the resulting fluid a few c.c. of pure nitric acid, meanwhile 

 keeping the test-tube cool by holding it under the tap. Crystals of 

 urea nitrate separate out if urea is present. Examine under micro- 

 scope (Fig. 154). 



VI. Uric Acid. Apply Murexide test (p. 258). 



VII. Blood Pigment. (1) Examine by means of the spectroscope. 

 A, the original fluid ; JB, the same after reduction ; C, the same 

 after the addition of caustic alkali and heating. By this latter 

 method alkali haematin is formed. This itself does not give a very 

 distinct absorption band, but if a reducing agent (NH 4 HS) be added 

 to it haemochromogen is formed, which has two very distinctly 

 marked bands in about the same position as those of oxyhaemoglobin. 



(2) Apply the guaiac and ozonic ether test (p. 277). 



When it is desired to ascertain whether Ferments be present it 

 is necessary to add a piece of coagulated egg-white, or of washed fibrin 

 to the original fluid, and to place the mixture on a water bath heated 

 to body temperature. If, after an hour, the digest gives a distinct 

 proteose reaction, and this was not obtained in the original fluid, the 

 presence of a proteolytic ferment may be assumed ; pepsin, if the 

 original fluid react acid, and trypsin, if it react alkaline. If proteoses 

 are present in the fluid itself, Mett's method (p. 450) must be employed 

 to identify the ferment. 



For the detection of Amylolytic and Steatolytic ferments, the 

 methods described on page 216 must be employed. 



For the detection, of the various substances which may occur in the 

 urine, the tests and reactions described in chapters xviii. and xix., 

 Part II., must be applied. 



SOME FORMS OF APPARATUS USED IN CHEMICAL PHYSIOLOGY 

 AND NOT ALREADY DESCRIBED. 



1. Folded Filter. Where rapid filtration of solutions containing proteids is 

 necessary, a folded filter should be used. This is made by folding the filter 

 paper into a quarter and then folding each quarter inwards on itself, so that each 

 is now divided into two. The filter is then completed by again folding each 

 portion in a direction opposite to the primary folds, by which means the paper 

 folds together like a fan. The folds are pressed, and then the fan is opened out, 

 and is ready for placing in the funnel (Fig. 278). 



2. Suction Filter. This is also used for rapid filtration". A strong triangular 

 flask with a side tube is fitted with an indiarubber cork, through which fits the 

 stem of a funnel. The funnel is provided either with an ordinarily folded filter 

 paper made of specially hardened paper, or it carries a small perforated porcelain 



