CHAP. II.] THE BLOOD. 45 



reagents : and that the blood and most other liquids of the body which 

 appear to coagulate spontaneously, only do so in consequence of their 

 containing at once fibrin and substances capable of reacting upon it and 

 so occasioning coagulation." 



Dr Buchanan then announced that he had found that the ad- 

 dition of that which he designated washed blood clot was most efficient 

 in inducing the coagulation of such liquids as do not coagulate spon- 

 taneously, but do so on the addition of blood. The 'washed blood 

 clot' he obtained by mixing one part of liquid blood with from six to 

 ten parts of water, and stirring carefully for five minutes. After the 

 mixture had stood for twelve or twenty-four hours, it was filtered 

 through a coarse linen cloth, and the substance left in the cloth 

 washed with water. 



When a small portion of this washed clot was reduced to frag- 

 ments and diffused through the liquid of hydrocele, coagulation 

 ensued, in many cases as rapidly as in the blood itself. The 

 washed coagulum retains, according to Buchanan, its coagulating 

 power for a long period, and with the addition of a little spirit of 

 wine may be kept for many months with its activity un- 

 impaired. 



"The power," Buchanan remarked, "which the washed clot has of 

 coagulating fibrin, is not less remarkable than that of rennet in 

 coagulating milk, to which indeed ifc may be aptly compared." 



The 'washed clot' of Buchanan is a mechanical mixture of 

 fibrin with colourless corpuscles. Upon which of these constituents 

 did its coagulant power depend? Buchanan concluded, from many 

 considerations, that this was seated in the colourless corpuscles. 

 He found that the buffy-coat of the blood of the horse, which is 

 exceedingly rich in colourless corpuscles, possessed a much greater 

 power of inducing coagulation, and preserved that power after being 

 kept for months and pulverized (from which statement we must con- 

 clude that the substance was dried). Moreover that the upper layers 

 of red clot which are comparatively rich in colourless corpuscles have 

 a stronger coagulating power than the lower layers. Furthermore 

 Buchanan found that many tissues of the body, muscle, connective 

 tissue and central nerve-organs possess, though in a much less degree, 

 the coagulant power, and he leant to the opinion that their influence 

 is seated in their cellular elements ('primary cells or vesicles'). 



To recapitulate: Buchanan held that the coagulation of the blood 

 is due to the conversion of a soluble constituent of the liquor san- 

 guinis into fibrin by an action exerted probably by the colourless 

 corpuscles and comparable to the action which rennet exerts in 

 effecting the coagulation of milk. Furthermore, that the liquid 

 which accumulates in certain serous sacs may be made to yield a 

 coagulum of fibrin when subjected to the action of liquids or solids 

 rich in the cellular elements with which the coagulant action ap- 

 peared to be associated. 



Although not altogether forgotten by a few individuals in England, 



