72 THE H^EMORRHAGIC DIATHESIS 



bleed from every slight abrasion, apart from any 

 family history of a similar kind. There is no doubt 

 that the symptoms and course of some of these cases 

 are identical with ordinary haemophilia,* and they 

 are nearly as common. Bulloch states that the 

 characteristic joint affections never occur except in 

 the hereditary class. 



PATHOLOGY OF HEMOPHILIA. 



Up to a certain point modern observers are agreed 

 as to the cause of haemophilia. Ever since Sir 

 Almroth Wright, nearly twenty years ago, showed 

 that the coagulation time in these patients is very 

 greatly delayed, all students of the disease who have 

 carefully fulfilled the proper conditions have been 

 able to establish his discovery. Normal blood in a 

 Wright's coagulimeter tube clots in five to ten minutes; 

 haemophiliac blood may take anything from fifteen 

 to ninety minutes to solidify, although the eventual 

 yield of fibrin is copious and firm. Addis has shown 

 that the coagulation time is exactly related to the 

 severity of the tendency to bleed, the mildest cases 

 yielding the shortest times, and the severe cases the 

 longest. It is true that a few who have used the blood 

 shed out during an actual haemorrhage have found 

 no delay in the coagulation time, but apart from 

 other fallacies, such as the danger of including fibrin 

 ferment, the mere fact of the continued bleeding 

 makes the blood clot more rapidly both in bleeders and 

 in ordinary people, as Wright and Addis have shown. 



* See instances given by Squire, Brit. Med. Jour., 1910, i., 

 p. 1168 ; and Osier, Lancet, 1910, i., p. 1226. 



