CHAP. II.] THE BLOOD. 29 



merely in having lost the fibrin-generators, which have united to form 

 fibrin. 



circum- ^he following circumstances hasten or promote co- 



stances which agulation : 



hasten Co- a. Exposure to a temperature higher than that 



agulation. of tlie living body (Hewson 1 , Hunter 2 , Thackrah 3 , 



Scudarnore 4 , Davy 5 , Gulliver 6 ), but probably not exceeding 52 C. or 

 54 C. 



b. Contact with foreign matter: thus the time of coagula- 

 tion will be affected by the shape of the vessel in which blood is 

 collected, the process occurring sooner where a large surface of blood 

 is in contact with the vessel, as for example when it is allowed to 

 flow into a wide shallow vessel. The influence of foreign matter ia 

 promoting coagulation will be again referred to. 



c. Closely connected with b. is the effect of agitation, which, 

 as Hewson 7 and John Hunter 8 shewed, and as has been fully con- 

 firmed, hastens coagulation. 



d. The dilution of blood with not more than twice its volume 

 of water (J. Hunter 9 , Prater 10 ). 



e. The addition of minute quantities of sodium chloride, 

 sodium sulphate or other neutral salt (Ancell 11 ). 



Conditions The following circumstances hinder or suspend co- 



which retard agu l ation .__ 



or suspend ^ -, , 



Coagulation. a - Exposure to a low temperature. 



Blood which is rapidly reduced to the temperature of 

 melting ice does not coagulate (Davy once kept blood fluid for one hour 

 at C.) : it may be frozen and remain in a frozen condition for hours 

 without losing its power, of coagulating when thawed (Hunter 12 , 

 Hewson 13 , Davy 14 ). It may be frozen and thawed several times in 

 succession without coagulating or losing its property of coagulating 

 (Davy). 



1 Hewson, Properties of the Blood, p. 3. The Works of William Hewson, F.E.S. 

 edited with an introduction and notes by George Gulliver, F.K.S. London, printed for 

 the Sydenham Society, 1846. 



2 Works, edited by Palmer, iii. 26, 110. 



8 Thackrah On the Blood, ed. 1834. Exp. 44, 45, 50, 51, 52, 56. 

 4 Scudamore On the 'Blood, p. 20. 8vo. London, 1824. 



3 Davy, Researches, Physiological and Anatomical. London, 1859, Vol. 2, p. 78. 

 Gulliver, Hewson 's Works, p. 4. Note in. 



7 Hewson, op. cit., p. 15. 



8 Hunter, Works, ed. by Palmer, Vol. in. 31. 



9 John Hunter, General Principles of the Blood, at p. 135 of Vol. in. of Palmer's 

 edition, of The Works of John Hunter. 



10 Prater, Experimental Inquiries in Chemical Physiology, p. 81. Part I. 'On the 

 Blood.' London, 1832. 



11 Ancell, Course of Lectures on the Physiology and Pathology of the Blood, &c. 

 Lecture VII. Lancet, 1839-40, p. 522. 



12 Hunter, Works of, by Palmer, Vol. in., p. 67. 



13 Hewson, op. cit., p. 17. 



14 Dr John Davy, op. cit., Vol. n., p. 75. 



