TEE MICROSCOPICAL REACTION 385 



18. Further dilutions in multiples of ten can be pre- 

 pared in the same way, and by varying the number 

 of volumes of diluting fluid or serum any required 

 dilution can be made (see Appendix, Dilution Tables) . 



NOTE. The saline diluting fluid must always be taken into the 

 pipette first, otherwise if the serum contains a very large amount 

 of agglutinin the traces of this serum added to the saline solu- 

 tion may be sufficient to entirely vitiate the subsequent observa- 

 tions whilst if more than one sample of serum is diluted from the 

 same saline solution serious errors may be introduced into the 

 experiments. 



The Microscopical Reaction : 



Apparatus Required: 



Five hanging-drop slides (or preferably two slides, with two cells 

 mounted side by side on each (Fig. 62, a), and one slide with one 

 cell only. 



Vaseline. 



Cover-slips. 



Platinum loop. 



Grease pencil. 



Eighteen to twenty-four-hour-old bouillon cultivation of the 

 organism to be tested (e.g., Bacillus typhi abdominalis) 



Pipette end with the remainder of the specific serum labelled s.s. 



Tubes containing the three solutions of the specific serum, 10, 

 i, and o.i per cent, respectively. 



Pipette end with pooled normal serum labelled p.s. 



METHOD. 



i. Make five hanging-drop preparations, thus: 



(a) One loopful of bouillon cultivation + one loopful 

 pooled serum; label "Control." 



(b) One loopful culture + one loopful undiluted 

 specific serum; label 50 per cent. 



Mount these two cover-slips on a double-celled slide. 



(c) One loopful bouillon culture + one loopful 10 

 per cent, serum; label 5 per cent. 



Mount this on single-cell slide. 



(d) One loopful bouillon culture + one loopful i per 

 cent, serum; label 0.5 per cent. 



(e) One loopful bouillon culture + one loopful o.i per 

 cent, serum; label 0.05 per cent. 



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