324 Addis 



I determined the coagulation time in tubes filled simultaneously and kept 

 under the same conditions. 



Two hundred and fifty-six estimations were made, and the average 

 difference in the coagulation time of each couple of comparable estimations 

 was found to be 30 seconds. The slight variations which exist in the 

 calibre of the tubes do not make any appreciable difference in the times, so 

 that half a minute represents the average error due to the deficiency in the 

 delicacy of the end-point. The average coagulation time was about 8 

 minutes. This amount of error is, I think, very much less than obtains 

 with the end-points adopted in other methods. 



Brodie and Russell's Method. 



The apparatus consists of a small circular chamber, floored with glass 

 and roofed in above by a metal ring, into which an inverted truncated glass 

 cone is fitted. A few drops of water are kept in the box, to lessen evapora- 

 tion. Surrounding the sides of the air chamber is a water-jacket with inlet 

 and outlet tubes for the circulation of water at a constant temperature. 



A small glass tube runs through the water-jacket and enters the air 

 chamber. It is so directed that when air is blown through the draught 

 impinges on the edge of the drop and causes the corpuscles to stream round. 

 This is repeated at short intervals, and the movement watched under the 

 microscope. Coagulation is considered to be present " as soon as a rim at 

 the periphery is solid, and blowing simply indents this rim, without causing 

 rotation." 



.In Bogg's(2) modification the water-jacket is discarded as unnecessary 

 and a more convenient form of box is adopted. Pratt (15) did not use 

 either the water-jacket or the glass cone, but simply directed a stream of 

 air on to a drop hanging from a glass slide. 



Brodie and Russell (1) themselves give only a few coagulation times 

 illustrating the effects of temperature. Pratt (15) found great variability 

 in the coagulation time, but was unable to discover the factors which led to 

 this. Murphy and Gould conclude that it is a more accurate method than 

 Wright's (17). They say that in 5 per cent, of the caSes no result could 

 be arrived at, because the blood would not flow at all. The times which 

 they obtained were very variable. Coleman (32) obtained very consistent 

 results by this method, working for the most part v/ith rabbit's blood. 

 Hinman and Sladen (36), after using Vierordt's, Hayem's, Wright's 

 and Milian's methods, came to the conclusion that Brodie and Russell's 

 was the best " as having the greatest accuracy, combined with simplicity of 

 technique." In 251 observations in health and disease, the limits were 

 from 33 minutes to less than 3 minutes. 



Widely variable times were recorded even in consecutive observations on 

 healthy people. 



I have made more than two hundred estimations with this method or 



