36 GENERAL ANATOMY. 



the blood, through, the veins at the root of the neck, disappears as the blood 

 passes through the lungs. 



The fluid part of the blood, the Liquor Sanguinis, or Plasma, is again com- 

 posed of a permanently fluid portion the serum and of fibrin, which coagu- 

 lates spontaneously when out of the body, but which is held in solution during 

 life. The fibrin can be separated from blood after it has been drawn by whip- 

 ping it with twigs, to which the fibrin as it coagulates adheres. The liquor 

 sanguinis may be obtained free from the red corpuscles "by mixing fresh-drawn 

 blood with six or eight times its bulk of serum, allowing the red particles to 

 subside, and then decanting the supernatant fluid and filtering it through blot- 

 ting paper" (Professor A. Buchanan, quoted by Dr. Sharpey). In this experi- 

 ment, or by removing a portion of the clear liquor which is found above the 

 bufi'y coat of inflammatory blood just after the latter has formed, the plasma 

 may be obtained (but diluted in the former method), and will then separate by 

 coagulation into a colorless clot of fibrin and a saline fluid. The former con- 

 sists of interlacing structureless strings, which contain in their meshes some 

 white corpuscles accidentally inclosed in them. The office and uses of the 

 fibrin, as well as its real nature, whether it exists as such in the living blood, 

 or is a product of the death of that fluid, have been and are the subjects of 

 much difference of opinion but such questions are exclusively within the do- 

 main of physiology. 



The fluid left after the coagulation of the fibrin, which is the serum of the 

 blood properly so called, is yellowish, and contains so much albumen that it 

 solidifies almost completely on being heated. It is alkaline from the presence 

 of free soda and carbonate of soda. The chemical composition of the blood is 

 complex, as might be anticipated of a fluid from which all the various tissues 

 of the body are to be formed; and it must of course vary in various parts of 

 the circulation. The following seems to be as accurate an analysis as possible. 

 It is quoted in the last edition of Carpenter's " Physiology" by Power, from M. 

 Gorrup-Bezanez, who procured two samples of the same person's blood, and 

 had them analyzed by himself and three other competent chemists. The sepa- 

 rate analyses are given, but the variations are too slight to be worth quoting. 

 The following were M. Gorrup-Bezanez's results : 



1st Spec. 2d Spec. 



Water ' . . 796.93 783.63 



Solid matters 203.07 216.37 



Fibrin 1.95 1.56 



Corpuscles 103.23 115.12 



Albumen 70.75 62.74 



Extractive matters and salts 27.14 36.95 



The crystals which form in the blood under certain circumstances and when 

 treated by certain reagents ought to be described, in consequence of their im- 

 portance as a means of distinguishing human from other kinds of blood. They 

 are of three kinds : 1. Hsematin crystals, found in normal blood, particularly 

 in the spleen. These are procured by the addition of a little water, or by agi- 

 tating the blood with ether, by either of which means the blood-corpuscles are 

 ruptured, and their contents crystallize on evaporation. 2. Haematoidifl crys- 

 tals, found in old clots. 3. Haemin crystals, formed by mixing dried blood 

 with an equal quantity of common salt and boiling it with a few drops of glacial 

 acetic acid till the whole has dissolved. A drop of the mixture placed on the 

 slide will show the crystals on cooling. Fig. 4 shows these three forms of 

 crystals from human blood together with some from the lower animals, for 

 comparison. 



The importance of being acquainted with the crystals found in human blood 

 is obvious, and more particularly those which can be obtained from dried 

 blood ; since in this way old blood-stains can be recognized as being human or 



