BLOOD. 2O7 



D and lying" somewhat nearer C than the band in the methaemo- 

 globin spectrum. Between D and F may be seen a rather indis- 

 tinct broad band: Dilute the solution until this band resolves itself 

 into two bands. Of these the more prominent is a broad, dark 

 absorption-band lying in the green between b and F. The second, 

 a narrow band of faint outline, lies in the light green to the red 

 side of E. A fourth very faint band may be observed lying on 

 the violet side of D. 



9. Acid Haematoporphyrin. To 5 c.c. of concentrated sul- 

 phuric acid in a test-tube add two drops of blood, mixing thoroughly 



. by agitation after the addition of each drop. A wine-red solution 

 is produced. Examine this solution spectroscopically. Acid hae- 

 matoporphyrm gives a spectrum with an absorption-band on either 

 side of D, the one nearer the red end of the spectrum being the 

 narrower. 



10. Alkaline Haematoporphyrin. Introduce the acid haemato- 

 porphyrin solution just examined into an excess of distilled water. 

 Cool the solution and add potassium hydroxide slowly until the 

 reaction is but slightly acid. A colored precipitate forms which 

 includes the principal portion of the hcematoporphyrin. The 

 presence of sodium acetate facilitates the formation of this precipi- 

 tate. Filter off the precipitate and dissolve it in a small amount of 

 dilute potassium hydroxide. Alkaline haematoporphyrin prepared in 

 this way forms a bright red solution and possesses four absorption- 

 bands. The first is a very faint, narrow band in the red, midway 

 between C and D ; the second is a broader, darker band lying across 

 D, principally to the violet side. The third absorption-band lies 

 principally between D and E, extending for a short distance 

 across E to the violet side, and the fourth band is broad and 

 dark and lies between b and F. The first band mentioned is the 

 faintest of the four and is the first to disappear when the solution 

 is diluted. 



VII. Instruments Used in the Clinical Examination of the Blood. 



i. Fleischl's Haemometer (Fig. 64, p. 208). This is an instru- 

 ment used quite extensively clinically, for the quantitative deter- 

 mination of haemoglobin. The instrument consists of a small cyl- 

 inder w^hich is provided with a fixed glass bottom and a movable 

 glass cover, and which is divided, by means of a metal septum, into 

 two compartments of equal capacity. This cylinder is supported 

 in a vertical position by means of a mechanism which resembles 



