CHAPTER V 

 THE PRESERVATION OF SERUMS METHODS 



IT is well to remember that serum collected shortly after a meal is 

 likely to be cloudy or opalescent; it is therefore advisable that blood 

 be collected several hours after eating or during a period of fasting. 



After securing a specimen of blood, the container should be set aside 

 and kept at room temperature until the serum separates. If the serum 

 is to be used at once, blood may be collected in centrifuge tubes, allowed 

 to coagulate, and then broken up, as gently as possible, with a sterile 

 glass rod and thoroughly centrifuged. On account of the mechanical 

 rupture of erythrocytes, such serums are usually tinged with hemo- 

 globin. After serum has separated from the clot it should be trans- 

 ferred to another tube, or, if this is not immediately possible, the con- 

 tainer should be placed in the refrigerator, to retard hemolysis, which 

 may soon occur and render the serum unfit for many purposes. 



Small amounts of serum are best removed from the clot with a cap- 

 illary pipet and teat, or with an ordinary graduated pipet with rubber 

 tubing and mouth-piece, in order that one may see exactly what he is 

 doing and not disturb the clot. As a perfectly clear serum is always to be 

 desired, serums mixed with corpuscles should be centrifuged. 



It may be stated, as a general rule, that all normal and immune se- 

 rums should be collected as aseptically as possible, and handled in a 

 careful and aseptic manner, so as to insure a clear and sterile product. 

 Notwithstanding the method of preservation all serums should be kept 

 in a refrigerator or ice-chest at a low temperature. 



PRESERVATION OF NORMAL SERUMS 



Normal serums that are to be used for purposes of immunization are 

 best preserved in small amounts in separate ampules, or in a large stock 

 bottle holding from 100 to 200 c.c. and well stoppered. In the produc- 

 tion of precipitin-serum, for example, sufficient serum of an animal may 

 be obtained at a single sitting for the whole course of injections, and this 

 serum is best preserved in separate ampules. Each ampule should 

 contain sufficient serum for one injection, and be sealed and marked. 



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