81 



LESSON IX 1 

 THE BLOOD 



Blood Plasma 



1. The coagulation of the blood has been prevented in specimen A by the 

 addition of neutral salt (an equal volume of saturated sodium-sulphate 

 solution, or a quaiter of its volume of saturated magnesium-sulphate solu- 

 tion). The corpuscles have settled, and the supernatant salted plasma has 

 been siphoned oflF. 



2. The coagulation of the blood in specimen B has been prevented by the 

 addition of an equal volume of a 0'4-per-cent. solution of potassium oxalate 

 in normal saline solution. 



3. Put a smaU quantity of A into three test-tubes and dilute each with 

 about ten times its volume of Uquid : 



A 1. With distilled water. 



A 2. With solution of fibrin ferment containing a little calcium chloride.* 



A 3. With the same. 



4. Put A 1 and A 2 into the water-bath at 40° C. ; leave A 3 at the tem- 

 perature of the air. A 1 coagulates slowly or not at all ; A 2 coagulates 

 rapidly ; A 3 coagulates less rapidly than A 2. 



5. Add to some of B a few drops of dilute (2 per cent.) calcium chloride 

 solution : it coagulates, and more quickly, if the temperature is 40° C. 



Blood Sermn 



Blood serum is the fluid residue of the blood after the separation of the 

 clot ; it is blood plasma minus fibrin. The general appearance of fibrin 

 obtained by whipping fresh blood will already be familiar to the student, as 

 he has used it in experiments on digestion (Lessons YI. and VII.). 



Serum has a yellowish tinge due to serum lutein, but as generally obtained 

 it is often contaminated with a small amount of oxyhaemoglobin, and so looks 

 reddish. It contains proteids (giving the general tests already studied in 

 Lesson II.), extractives, and salts in solution. The proteids are serum 

 albumin and serum globulin. The fibrin ferment is also a proteid-Uke sub- 

 stance. It is present in only small quantities, and in the following experi- 

 ments is precipitated with serum globulin. 



' This lesson may conveniently be divided into two, the first dealing with 

 plasma and serum, and the second with htemoglobin. 



- An easy way of preparing an impure but efficient solution of fibrin ferment 

 is to take 5 c.c. of blood serum and dilute it with a Utre of distilled water. A 

 partial precipitation of globuhn takes place, and carries down the ferment with it. 

 After a few hours pour off the supernatant fluid and dissolve the precipitate in 

 half a litre of tap water to which a few drops of 2 per cent, solution of calciiun 

 chloride have been added. This solution can be then given round to the class as 

 fibrin ferment. 



