BLOOD, g 



principles of the blood. Among these, principles are lime, 

 ammonia, soda, potash, phosphorus, magnesia, iron and other 

 metals in the form of salts; chlorides, sulphates, carbonates, 

 phosphates, &c.; and mingled with these are the principles 

 of the secretions and organic substances, of which the most 

 important, from their quantity, are fibrine, 2-5 parts in 1000, 

 and albumen 69 to 70 in 1000. 



The blood owes its colour to the red corpuscles, which are 

 themselves coloured by a substance which De Blainville has 

 named hematosine, and which contains 7 parts in i oo of iron. 

 These corpuscles are round flattened disks of *oo6 to '007 

 of a millimetre in diameter, and a thickness of '002 milli- 

 metre. Under the microscope they appear grouped together 

 without order, or piled one upon another like pieces of 

 money, and are of a red colour in reflected light. The white 

 corpuscles are smooth, spherical, of a yellowish-white colour 

 in a reflected light, and from '008 to "014 of a millimetre in 

 diameter. 



The colour of the blood is a beautiful crimson red in the 

 arteries, but of a darker colour in the veins. We shall have 

 occasion to examine it from this point of view in treating of 

 the circulation. 



When blood which has been drawn is allowed to stand in 

 the vessel, it separates into two distinct parts : the one, semi- 

 solid, is called the crassamentum the clot; the other fluid, 

 is called serum. The clot is the coagulated fibrine which 

 carries with it the red globules which were held in suspension 

 in the blood. When the coagulation is delayed, these glob- 

 ules, being heavier than the other portions of the blood, fall 

 toward the lower part of the vessel; and the fibrine, freed 

 from them, coagulates and retains its own proper colour, and 

 the clot is composed of two layers the superficial layer is 

 of a grayish or white colour and semi-transparent, and is 

 termed the "buffy coat." It is formed of pure fibrine mingled 

 with the white globules; the other is composed of fibrine and 

 of the red globules which give it its colour. The serum 

 is a transparent, greenish-yellow fluid, sometimes a little 

 whitened by minute fatty specks; from which circumstance, 

 and from some other points of analogy between them, it has 



