210 Original Articles. [April, 



on the whole it is an excellent example of a connecting link between 

 substances that are really dissolved by water, and those which can 

 only be disseminated through it in comparatively large particles. 



If ammonia be added to a solution which would give such a spec- 

 trum as No. 4, we obtain one like No. 5. The band in the red dis- 

 appears, those in the green become far more distinct, and the spectrum 

 is similar to that of fresh blood, only the bands are more faint, and it 

 is slightly shaded up to £ above D. 



If a small quantity of a strong solution of this brown cruorine be 

 placed on a piece of glass, and allowed to evaporate slowly, the greater 

 part collects as a dry film round the outside of the drop ; and, when 

 examined on the stage of the microscope, it yields a spectrum like 

 4 or 5, accordingly as it is damp or quite dry. If dry, the spectrum is 

 very similar to that of fresh blood, only the absorption-bands are less 

 distinct ; but, when breathed on, so that it may again become damp, 

 the dark band in the red makes its appearance, and those in the green 

 become more faint. These changes take place over and over again, 

 though they gradually cease after some days ; and hence it would ap- 

 pear that the dark band in the red depends on the presence of moisture, 

 and may be due to the formation of some hydrous compound, decom- 

 posed on drying. The scarlet cruorine of fresh blood, treated in the 

 same manner, exhibits no such changes, and gives the same spectrum 

 as its solution in water. 



Drying solutions of blood on glass in this manner gives very satis- 

 factory results, and specimens so prepared may be kept in that state, 

 or under thin glass fixed down with Canada balsam, without there being 

 any sensible alteration after above half-a-year. The solution may be 

 placed on a small square of thin glass till it has evaporated and 

 become reduced to a drop or so, and then, having redissolved the dry 

 part in the liquid, it may be allowed to run off at one corner to the 

 glass on which it is to be kept, leaving the minute foreign fragments 

 behind. If, however, the mordants used in dying the fabric have 

 changed the blood to hfematin, the results are not satisfactory. A 

 solution of fresh blood mounted in a cell still gives the characteristic 

 spectrum after some months, though more faintly than at first. 

 Brown cruorine soon forms a deposit, and loses its character when 

 thus kept. 



Professor Stokes has described the change produced by the action 

 of deoxidizing agents on fresh blood. Whether the cruorine be fresh 

 and scarlet, or have been more or less converted into the brown 

 modification, if citrate of ammonia be added to an alkaline solution, 

 so as to prevent the precipitation of oxide of iron, and then, having 

 introduced it into a cell, if a small piece of crystallized protosulphate 

 of iron be added, and broken up and stirred till dissolved with a 

 platinum wire flattened at one end and bent at right angles so as to 

 form a sort of little hoe, we obtain the spectrum No. 6. There is one 

 well-marked absorption-band, the centre of which is 1| below D, and 

 a general shading upwards as far as D. Hence it is clear that the 

 change from scarlet to brown cruorine is not of such a nature as to 

 prevent both from yielding the same spectrum when deoxidized ; or, 



