582 [June 11, 



process of coagulation ; and secondly, as to the cause of its occur- 

 rence when the blood is removed from the body. 



. With regard to the first point, the essential nature of the process 

 of coagulation, different views have been entertained. John Hunter 

 was of opinion that the coagulation of the blood, the solidification of 

 the fibrin, was an act of life analogous, in some respects, to the 

 contraction of muscular fibre. This, on the other hand, was made 

 very unlikely by the observation of his contemporary, Mr. Hewson, 

 that blood may be kept in the fluid state by the addition of various 

 neutral salts, but retains the faculty of coagulating when water is 

 added to the mixture. Mr. Gulliver, on one occasion, kept blood 

 fluid, by means of nitre, for upwards of a year, but found that it 

 still coagulated on the addition of water. It seems exceedingly im- 

 probable that any part of the human body should retain its vital 

 properties after being thus pickled for more than a year. But here 

 I would wish to make an explanation of the use of this term " vital 

 properties." When employing it, I do not wish to commit myself 

 to any particular theory of the nature of life, or even to the belief 

 that the actions of living bodies are not all conducted in obedience 

 to physical and chemical laws. But it appears that every compo- 

 nent tissue of the human body has its own life, its own health, just 

 as we ourselves have ; and as the actions of living men will ever re- 

 tain their interest whatever views be entertained of the nature of 

 life, so must the actions of the living tissues ever continue to be 

 essential objects of study to the physiologist and pathologist. When, 

 therefore, I use the term "vital properties," I mean simply proper- 

 ties peculiar to the tissues as components of the healthy living 

 body. 



Turning now to the other aspect of the subject of coagulation the 

 cause of the occurrence of that process on the escape of the blood 

 from the living body we find that here again various theories have 

 been held, which may be divided into mechanical, chemical, and 

 vital. The mechanical theory was, that mere rest of the blood was 

 sufficient to cause coagulation. I say this was the theory; but I 

 believe it will be found to be still taught by many, that the cause 

 of the coagulation of the blood in an artery which has been tied is 

 its stagnation in the vicinity of the ligature. 



As to the chemical theories they have been various. One very 



