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LXXIII. Outliyies of a Philosophical Inquiry into the Nature 

 and Properties of the Blood; being the Substance of three 

 Lectures on that Subject delivered at the Gresham Institution 

 during Michaelmas Term 1826. By John Spurgin, M.D. 

 Fellow of the Royal College of Physicians of London^ and of 

 the Cambridge Philosophical Society. 



[Continued from p. 207.] 



"'I^/''HEN blood is drawn from the body, as from a vein of 

 ^ ^ the arm, it presents the obvious characters of fluidity 

 and redness, and to the touch is warm and shghtly viscid ; 

 after remaining at rest, however, for about seven minutes, it 

 begins to separate into two distinct portions ; the one yellow- 

 ish and fluid, and occupying the surface of the mass ; the 

 other red and solid, and tending to the bottom of the vessel 

 that contains it. This change is denominated the coagulation 

 of the blood ; the watery part is termed the serum, and the red 

 and denser part the crassamentum, coagulum, or clot. 



In order to our obtaining a more particular or intimate 

 knowledge of these now separate parts of the blood, Ave must 

 avail ourselves of the experiments and observations which have 

 been recorded by various authors upon whom we can place the 

 greatest I'eliance. We learn then from these, that the serum 

 is an apparently homogeneous fluid of a yellowish colour, unc- 

 tuous to the touch, and saline to the taste; that its specific 

 gravity is very variable, but on the average is about 1029, water 

 being 1000; whilst that of blood fresh drawn, and therefore 

 in its more natural state, is about 1050. When exposed to 

 a heat of 160° of Fahrenheit, it is converted into a somewhat 

 firm white mass which is designated coagulated albumen, and 

 which on being cut into slices and subjected to gentle pres- 

 sure, gives out a small quantity of a slightly opaque licjuor, of 

 a saline taste and peculiar odour, which is called the serosity, 

 consisting of water, pure soda holding albumen in solution, of 

 muriate of soda, or common salt, muriate of potash, slight traces 

 of phosphoric acid, besides lactate of soda, and animal matter. 

 When serum is evaporated at a heat below that required for 

 its coagulation, it yields a yellowish semitranspai'ent mass re- 

 sembling amber, that splits into pieces in drying, and amounts 

 to about 95 grains from 1000 of serum. But not only is the 

 serum permanently coagulated by heat, but also by the mine- 

 ral acids ; and the insoluble compounds thence produced ex- 

 actly resemble those of the same acids with the fibrin of the 

 crassamentum, on wliich we shall have to speak presently : 

 and as alcohol produced similar effects with both these mat- 

 ters, 



