1897J MICROSCOPICAL JOURNAL 137 



should have a faint reddish ting^e. The cover-<^hiss, with 

 the mixture on the surface, is inverted over a hollow slide 

 (the edg-es about the concavity having 1)een smeared with 

 oil or fiuid vaseline so as to make a closed chamber), and 

 the hang-ing drop then examined under the microscope 

 (preferably by gas lig-ht), a iiigh-power dry lens (about 1-6 

 inch) being- used. 



If thereaction takes placerapidly, the first glance through 

 ■the microscope reveals the completed reaction, all the ba- 

 cilli being in loose clumj^s and nearly or altog-ether motion- 

 less. Between the clumps are clear spaces containing few 

 or no isolated bacilli. 



If the reaction is a little less complete, a few bacilli may 

 be found moving slowly between the clum])s, in an aimless 

 way, while others attached to the clum])s by one end are 

 apparently trying to pull away, much as a fly caught on a 

 ffy-paper struggles for freedom. 



If the agglutinating substances are still less abundant, 

 the reaction may be watched throug-h the whole course of 

 its development. Immediately after mixing- the blood and 

 culture together it will be noticed that manv of the bacilli 

 move more slowdy than before the addition of the serum. 

 Some of these soon cease all progressive movement and it 

 will l)e seen that they are g-athering together in small 

 groups of twoor more, theindividual bacilli being still some- 

 what separated from each other. Gradually thev close up 

 the spaces between them and clumps are formed. Accord- 

 ing to the completness of the reaction, either all the bacilli 

 may finally t)ecome clumped and immobilized or onl\- a 

 small ])ortion of them, the rest remaining freeh' motile, 

 and even those clumped may ai)pear to be struggling for 

 freedom. With blood containing a lai-ge amount of the 

 agg-lutinating sul)stances all gradations in the intensitv of 

 the reaction may be ol)servetl, from those shown in a 

 marked and immediate reaction to those appearing- in a late 

 and intletinite one. b\- simply \ar\ing the pi'oportion of 

 blood adiU'd to the culture lluid. 



Pseudo Re-actions With Dried Blood. 11 to.) eon- 

 .•entrated a solution of dried blood fi-oin a healtiiv person 



