the Colour of the Blood during Coagulation. 359 



the green produced precisely the same vermilion figures. 

 Finding this to he the case, I determined to ascertain, as far 

 as I had an opportunity of doing so, whether, and to what ex- 

 tent, any other colours produced a similar effect ; for as yet I 

 had seen no change from contact with any colour excepting 

 green. My interest was still further increased, by understand- 

 ing from Dr Abercrombie that he had made a similar remark. 

 With this view I procured a variety of cups, with devices of 

 various colours decorating their interior ; and these I used in 

 many cases in which I had occasion to draw blood, but with- 

 out succeeding in obtaining any change of colour upon the 

 coagulum, except from the green. This was invariable, pro- 

 vided the colour was decided and brilliant ; the impression 

 on the clot being always an accm"ate representation of the 

 ornament on the cup. The result of these observations I com- 

 municated in a short notice I read to the British Association 

 at their meeting in Dublin in August 1835. 



Owing to an absence abroad, it was not till lately that I 

 had an opportunity of resuming my inquiries into the subject. 

 During the last two or three months, however, I have made a 

 considerable number of experiments, under various circum- 

 stances, with the view of ascertaining some of the conditions 

 which affect the result. 



I procured a considerable number of cups, with devices of 

 different descriptions both as regards figure and colour, and 

 subjected them to the usual method of making such observa- 

 tions, as often as a suitable case presented itself In order 

 also to trace if possible any connection, if such existed, betwixt 

 the substances of which the ornament was composed, and the 

 appearance on the blood, I obtained, through the obliging 

 introduction of Mr Child of this city, a communication from 

 Mr Ridgway of Staffordshire, giving much practical informa- 

 tion as to the different ingredients which are used in orna- 

 menting china. From him I learnt, that the bright green 

 colour is composed of the green oxide of chrome, and laid on 

 as a pigment in the usual way. Whilst another and very 

 common method of ornamenting china was, by laying upon the 

 biscuit previous to its being glazed, a device printed and co- 

 loured upon paper. By this mode there is no perceptible ele- 



