BLOOD. 



217 



Comparison of the venous blood ivith the blood of the capillaries. 



It is well known that blood taken from the body by scari- 

 fication does not materially difter in its physical properties 

 from venous blood ; it takes about an equal time to coagulate^ 

 and separates into clot and serum. The blood which flows 

 from leech-bites is also similar to venous blood. From com- 

 parative analyses of venous blood and blood taken by leeches 

 or cuppiugj Dr. Pallas^ concludes that the (so termed) capillary 

 blood is richer in solid and coagulable constituents than either 

 venous or arterial blood. 



The ratios are represented by the following numbers : 



2-550 : 3-100 and 



3-550 : 2-630 



Denis^ contradicts these statements; he obser\^es that the 

 blood of the capillaries, when taken by cupping, is of a bright 

 red colour and very plastic if it is taken from the neighbour- 

 hood of a large artery, but that it is dark and proportionally 

 less plastic when drawn from the vicinity of large venous trunks; 

 so that its characters always present a certain degree of simi- 

 larity to either arterial or venous blood. Denis analysed blood 

 drawn from the arm of a man aged 70, and blood taken by 

 cupping from the left side of the thorax of the same individual, 

 and compared the results. 1000 parts contained : 



