THE EXAMINATION OF MICRO-ORCANISMS 613 



Reduced hcTmoglobin shows one broad band between lines D 

 and E. 



Metha^moglobin sliows two equal bands between D and I{ and one 

 between C and D. The urine is brown. It is often seen in mild cases 

 of blackwater fever. 



Urobilin shows one broad band between E and F. 



THE TONICITY OF THE BLOOD. 



Some specimens of corpuscles have the power of retaining hb. 

 better than others. Distilled water will remove the hb. but saline 

 solution over a certain strength will not remove it. The resistance 

 or tonicitv can be measured by the strength of that saline solution 

 which is just sufiticient to prevent the solution of the hb. This 

 solution is said to be " isotonic." Normal blood is hypertonic. 



Normal saline solution, 75 per cent., prevents the solution of the hb. 



Make a series of weaker solutions differing o"02 per cent. 



Place one drop of blood in this, shake and allow to stand. 



The weakest saline solution that does not cause solution of the hb. 

 is the index of the tonicity of the blood used. The normal is o"46 to 

 0*48 per cent. 



A decrease of tonicity often precedes a h^emolytic attack. 



Persons of a normally low tonicity should not be allowed to live 

 where blackwater fever is endemic. 



THE ENAAIINATIOX OF ?^IICRO-ORGAXISAlS. 



TO STAIN MICRO-ORGANISMS. 



The Gram method is important. 



To Stain Smears. 



Stain witli aniline gentian violet, five minutes. 

 Pour off, treat with Gram's iodine solution, two minutes. 

 Pour off, treat with alcoholic eosin until the colour ceases to come 

 out freely. 



Wash, dry and mount. 



Gram's iodine is i part of potassium iodine and 300 parts of water. 



Jo Stain Sections. 



Stain with aniline and gentian violet, ten minutes. 



Stain with Gram's iodine, two minutes. 



Pour off and blot. 



Stain with alcoholic eosin, thirty seconds. 



Oil of cloves and xvlol. 



