BLOOD. 77 



and allow it to evaporate to dryness. Then add a very small 

 drop of blood and two drops of glacial acetic acid and cover 

 with a glass. Warm cautiously until bubbles of gas begin to 

 form in the mixture under the cover-glass. Examine and 

 sketch under the microscope. The hsemin crystals are rhom- 

 bic plates, brown in color by transmitted light. In large 

 masses they have a metallic lustre and appear steel-blue by 

 reflected light. 



Spectroscopic Examination. 



(a) Oxyhcemoglobin. Dilute 1 c.c. of blood with 200 c.c. 

 of water. Examine spectroscopically. At this dilution one 

 broad absorption-band is seen extending from the D line 

 (588) to b (518). The violet end of the spectrum is also 

 absorbed as far as the F line (486). Upon again diluting 

 this solution with an equal volume of water it is noticed that 

 the broad band has resolved itself into two, the one next to D 

 being narrower and more intense than the broader one to the 

 right. Between the two bands is a green interspace. Less 

 of the violet end is now absorbed. Upon still further dilu- 

 tion, the bands become narrower and finally disappear simul- 

 taneously. 



(6) Hcemoglobin (Reduced Hcemoglobiri). Prepare some 

 Stokes' reagent as follows: Dissolve 3 grams of ferrous sul- 

 phate in a small quantity of water and add to it in watery 

 solution 2 grams of tartaric acid. Make up the mixture to 

 100 c.c. and just before using add NH 4 OH until the precipi- 

 tate which at first forms is dissolved. This solution of 

 ammonium ferrotartrate is a reducing agent, removing the 

 oxygen which is in weak combination with the oxyhaBmoglo- 

 bin, and thus forming hemoglobin. To the blood, 200 times 

 diluted, add a few drops of Stokes' reagent. Notice the 

 change in color. Examine in the spectroscope. A broad, 



