22 LABORATORY COURSE IN SERUM STUDY 



(6) Place the tubes in the incubator for two hours, and then 

 pour into each tube a tube of agar which has been melted in 

 boiling water and cooled to 42 C. Pour the entire contents 

 of each tube into a sterile Petri dish. When the plates are 

 hardened, place them in the incubator in an inverted position, 

 to be observed at the following lesson. The plates made from 

 tubes 2 and 3 will show an enormous number of minute 

 typhoid colonies after incubation. The plate from tube 1 will 

 be sterile or may show a few large colonies. 



ILEMOLYTIC AND ILEMAGGLUTINATIVE POWER OF 

 NORMAL SERUM 



The normal blood serum of many animals has haemolytic 

 and haemagglutinative action upon the red blood cells of animals 

 of some other species. This hsemolytic action, like the bacteri- 

 cidal action, is lost when the serum is heated to 56 C. The 

 haemagglutinating property, on the other hand, is relatively 

 resistant to heat and is not destroyed until the serum is heated to 

 70 C. or above. Such a hsemolytic normal serum acts only on 

 the erythrocytes of certain other species, sometimes upon 2 or 3 

 varieties with differing intensity. Thus goat serum is strongly 

 haemolytic for rabbit cells less so for those of guinea pigs. 

 Dog serum contains a relatively large amount of normal haemo- 

 lysin for most cells used in laboratory work. Guinea pig cells 

 are highly susceptible, and human cells relatively resistant to 

 haemolysis by dog serum. 



Reagents : 



1. Fresh dog serum. 



2. 2 % suspension of washed guinea pig cells. 



3. 2 % suspension of washed human cells. 



4. Salt solution. 



Place 0.25 c.c. of dog serum in a test tube and heat for one half 

 hour in water bath at 56 C. Bring up volume to 2.5 c.c. with normal 

 salt solution. Prepare a similar 1-10 dilution of unheated dog serum. 

 Set up the following experiment in half-inch tubes : 



