CHEMICAL BASIS OF THE ANIMAL BODY. 1299 



limited to the spectroscopic appearances which they present 

 either in situ in the mother-tissue or in solutions obtained by 

 the action of ether, while their respiratory function is assumed 

 from the changes which they exhibit under the influence of 

 reducing agents and subsequent exposure to oxygen. Of these 

 histohsematins the one most fully described is known as myo- 

 hifimatin from its characteristic presence in muscles. 



Myohcematin. To observe the spectrum of this substance a 

 slice of tissue, such as that of the heart, is squeezed in a com- 

 pressorium until sufficiently thin to transmit light. It is then 

 examined with a microspectroscope under strong illumination. 

 Or, on the* other hand, the tissue may be treated with excess of 

 ether, under whose influence an aqueous juice is extruded in 

 which the myohsematin is in solution. Speaking generally, for 

 the appearances vary slightly according to the source of the 

 pigment, myohcematin yields a four-banded absorption spectrum. 

 The first band lies close to D, but towards the red end of the 

 spectrum. The next two bands are situated close together 

 about midway between D and E. The remaining band lies in 

 the region between E and b. Solutions of myolnematin are 

 when weak of a reddish-yellow colour, but if strong they are 

 pure red. By the action of warm alcohol containing a little 

 sulphuric acid a spectrum is obtained closely similar to that of 

 hsematin in acid solution, and by the use of concentrated sul- 

 phuric acid a substance is produced which in both acid and 

 alkaline solutions shews bands similar to those of hsematopor- 

 phyrin in the same solvents. Under certain conditions myo- 

 haematin becomes 'modified' and now yields two bands similar 

 to those of hflemochromogen, but situated nearer the violet end 

 of the spectrum. 



The conclusions drawn from the above spectroscopic facts have 

 been the subject of some controversy and adverse criticism, the 

 appearances being regarded as due not to a specific pigment, but 

 rather to haemochromogen or mixtures of other products of the decom- 

 position of haemoglobin. 



11. Haemin. 1 C 34 H 35 N 4 Fe0 5 . HC1. (HaBmatin-hydrochlo- 

 ride or Teichinann's crystals.) 



These crystals may be readily obtained for microscopic 

 examination by heating a drop of fresh blood on a glass slide 

 under a cover-slip with a little glacial acetic acid. In the case 

 of blood which has been dried, as in an old blood clot or stain, 

 the residue should be powdered as finely as possible with a 

 minute quantity (trace) of sodium chloride. A little of the 

 powder is then placed on a slide and covered with a slip 



1 According to more recent work the formula of true haemin is C32H3oN 4 Fe03, 

 the crystals being a hydrochloride of this substance. 



