the Colour of the Blood during Coagulation. 361 



which was thus formed, after the upper surface, exposed to the 

 air, had assumed the red colour, it was found that the rest of it, 

 in contact with the interior of the cup, presented the leaden 

 colour, without any trace whatever of change of tint on the 

 part corresponding with the green ornaments. Unsuccessful 

 in this, in order to assist me to estimate how far the other 

 condition which I had observed, namely, the partial elevation 

 of the green ornament, was connected with the result, I had 

 artificial elevations made in the interior of the cup, by fixing 

 a small piece of wood of the size of a button mould in the 

 bottom of it, covered with copal varnish. During repeated 

 experiments, the only eff'ect from this was a depression coi-- 

 responding to the elevation, but no perceptible change of 

 colour. Still further to test how the effect might be produced 

 by the impression of the elevation on a coloured surface, I 

 substituted isinglass coloured with cochineal, which, when co- 

 agulated, and inverted, somewhat resembles the clot of blood. 

 In this instance there was a depression corresponding to the 

 elevation of the green ornament, but no change of tint. 



Satisfied that the appearance could not be accounted for 

 by any mere mechanical effect produced by the impression of 

 the elevation, it occiu-red to me that possibly the blood in coa- 

 gulating might so arrange its particles in relation to the orna- 

 ment, as to produce the phenomenon described. With a view 

 to test this, I drew blood into a plain white cup, and, after com- 

 plete coagulation, removed the clot into one whose decoration 

 had on many occasions given the vermilion colour. After 

 allowing it to remain here for some hom\s, I again inverted it 

 in the usual way, and procured a most accurate and beautiful 

 representation of the ornament as in my first observations. 

 Tlus of course entirely contradicted this hypothesis. 



Thus far in my observations I had remarked nothing to 

 disturb my conviction of the appearance being connected with 

 the colour of green. In no instance, and I had made upwards 

 of sixty observations since I first noticed the circumstance, 

 had I been able to observe the slightest difference of tint, when 

 the ornament was of another colour. Upon a recent occasion, 

 however, when employing a small cup with the device of a 

 flower, of a pinkish or crimson colour, darker towards the cir- 



