372 Dr. Spurgin's Outlines of a Philosophical 



into a substance which possesses the physical and chemical 

 properties of jelly*. 



With regard to the red and denser part that forms or se- 

 parates spontaneously from the more fluid part or serum, which 

 in contradistinction to the serum is called the cruor or clot, it ap- 

 pears to the eye, generally, under the form of a soft solid, of such 

 consistence as to bear cutting with a knife, and to be of a fibrous 

 and reticulated structure. The colour of this fibrous mass 

 may be washed away or separated by repeated ablutions in 

 water, and the mass will then be found to be made up of a white 

 shred-like matter, apparently deriving its colour from a sub- 

 stance distinct from itself, or from a colouring ingredient 

 which is only mechanically mixed with it, and not retained 

 by any chemical affinity. When this shred-like matter is 

 thus procured in a pure state, it is found to be a solid of 

 considerable consistence, elastic and tenacious, and in its ge- 

 neral aspect as well as in its chemical relations very similar 

 to the pure muscular fibre. It has been designated by several 

 names ; as the coagulable lymph, gluten, fibre of the blood, and 

 fibrin. Upon this substance the spontaneous coagulation of 

 the blood depends. Many are the experiments which have 

 been made with the view of ascertaining the circumstances 

 which peculiarly affect or produce this spontaneous change of 

 the blood, or which influence it in any way either to retard or 

 to promote it : but it is not requisite to adduce in this place 

 all the modes resorted to for the purpose, nor all the results 

 that have been olitained ; but suffice it to saj^, that rest chiefly 

 conduces to its coagulation, whilst free agitation and the ad- 

 dition of certain neutral salts will either retard it or prevent it 

 altogether. The experiments of Mr. Hewson on the coagu- 

 lation of the blood are very interesting, inasmuch as they show 

 that this tendency is modified by various circumstances, even 

 in the living body; and he was enabled to conclude fi'om them, 

 that any thing which tended to impair the strength of the 

 body, — as large bleedings, faintings, &c. — seemed to increase 

 the tendency to coagulation f ; as also certain passions of the 

 mind, — the depressing passion fear more especially. Whilst, on 

 the contrary, any thing which increased the action of the ves- 

 sels, or in other words excited the body, lessened this tendency 

 very considerablj' : indeed, his experiments led him to think 

 that the properties of the blood depend on the action or state 

 of the blood-vessels, or " that they have a plastic power over it, 

 so as to be able to change its properties in a very short time|." 

 In inflammations, when the blood-vessels are acting more 



* Bostock's Elements of Physiology, vol. i. p. 473. 



f Hewson's Experimental inquiries, p. 126. X ^^^^- P* ^^7" 



strongly, 



