THE BLOOD. 233 



The coloring matter may be separated completely from the 

 Crassamentum by washing it with water. 



The blood, therefore, consists of three parts, namely ; the 

 Serum ; the substance which coagulates spontaneously 

 (fibrine) ; and the Coloring Matter. 



If the blood be examined with the microscope in the 

 vessels of a transparent part, or immediately after it has flowed 

 from the body, it is seen to consist of small red particles or 

 globules, and a clear-colorless fluid. This fluid is the lympha 

 or liquor sanguinis, and must not be confounded with the 

 serum, which separates from the crassamentum during coagula- 

 tion. It can be obtained free from the red globules, before coagu- 

 lation takes place, by filtering the blood of a frog or some other 

 animal, in which the red globules are so large as not to pass 

 through the pores of the filtering paper. The liquor sanguinis, 

 consists of the serum of the blood that holds the fibrine, which 

 is also colorless, in a state of solution. When the fibrine coagu- 

 lates, it encloses within it the red particles, and the watery 

 part of the blood (serum) is left, which holds the albumen in 

 solution. 



The Serum 



Has a considerable degree of consistence, although it is much 

 thinner than blood. In its perfectly natural state, it is almost 

 transparent, and appears to be very lightly tinged with a 

 greenish yellow color; but it is very often impregnated with 

 a portion of bile, which is probably carried to the blood-vessels, 

 by the absorbents. It contains a large quantity of albumen, 

 or matter like the white of an egg. If heated to 140 of Fah- 

 renheit, it becomes opaque ; and when the heat is increased to 

 156 or 160, it is firmly, coagulated. It is also coagulated by 

 alcohol, by mineral acids, and by rennet.* It is proved by 

 chemists, that it contains a small quantity of pure soda. It 

 therefore changes several of the blue colors of vegetables to 

 green. It is also found to contain a similar quantity of the 



* See Hewson, vol. i. 139. I suspect that some particular management is 

 necessary in the use of rennet. 



20* 



