456 APPENDIX 



mine it. The control should be titrated before the test solution acted upon by the 

 urease and the shade of the test solution should correspond to the control. About 



2 drops of a 0.05% aqueous solution of methyl orange should be used for 50 c.c. of 

 test solution. 



Hydrogen-ion Concentration of the Blood. Levy, Rowntree and Marriott have 

 proposed this determination as an index of the reaction of the blood. The test 

 may be made either on oxalated blood or with serum. The hydrogen-ion concen- 

 tration of the serum of normal persons varies from p H 7.6 to p H 7.8, that of oxa- 

 lated blood from p H 7.4 to p H 7.6. The exact point of neutrality, p H 7, is only 

 reached in severe uncompensated acidosis and a reaction of p H 8 is only possibly 

 obtainable after administration of alkalis. 



One to 3 c.c. of clear serum or of blood is run, by means of a blunt-pointed 

 pipette, into a dialyzing sac which has been washed inside and outside with salt 

 solution and which has been tested for leaks by filling with the salt solution. The 

 sac is lowered into a small test-tube (100 x 10 mm., inside measurements) containing 



3 c.c. of the salt solution, until the fluid on the outside of the sac is as high as on the 

 inside. From five to ten minutes are allowed for dialysis. The collodion sac is 

 removed and five drops of the indicator (an aqueous 0.01% solution of phenol- 

 sulphonphthalin) are thoroughly mixed with the dialysate. The tube is then com- 

 pared with the series of standards until the corresponding color is found, which 

 indicates the hydrogen-ion concentration present in the dialysate. 



These tests may be carried out with 3 c.c. of blood or serum. The same results 

 are obtained with i c.c. of blood or serum on the inside of the sac, and with this 

 amount it is immaterial whether there is i or 3 c.c. of salt solution on the outside. 



For the comparison of tubes with standards a good light (natural or artificial) 

 and a white background are requisites. Readings must be made immediately. 

 The tube matching most closely is selected and also the tubes on either side of it. 

 These are critically inspected against a white background. Changing the order 

 of the tubes often makes differences more apparent. 



Hynson, Westcott and Co. prepare a set of standards with the h drogen-ion con- 

 centration marked on each ampule. The dialyzing collodion sacs are made as for 

 the Abderhalden test or they may be purchased. 



E CHEMICAL EXAMINATION OF URINE 



For the prevention of decomposition when a urine is not examined shortly after 

 voiding, chloroform (10 to 20 drops added to a tightly corked bottle) or formalin 

 (4 or 5 drops to a pint of urine) are ordinarily employed. Formalin is better for 

 microscopical material, but, owing to its reducing power, should be substituted by 

 boric acid in urine to be examined for sugar. For clearing urine, turbid by reason 

 of bacteria, rubbing up with Talcum purificat., U. S. P., and filtering is recom- 

 mended. // is advisable to call for a fresh specimen and not to examine a decomposed 

 urine either for casts or albumin, 



A twenty-four-hour specimen is necessary for accurate work. The urine should 

 be collected in clean separate bottles. Where pus comes from the bladder the 

 proportion of pus in each bottle will be practically the same; if from the kidneys 

 the amount will vary in the different bottles. 



ter 



