BY A. JEFFERIS TURNER, JI.D., LOND. 27 



vibrio, though in most respects exactly resenibhng it. Here 

 then was a new method of distinguishing the true cholera vibrio 

 from its counterfeits. The exact method used by Pfeiffer need 

 not concern us ; it has since been much simplified. For the 

 distinction of typhoid from other similar bacilli an identical 

 procedure has been found of the greatest value. 



But, it has been discovered by Widal and others, that our 

 reaction has a double value. It is, so to speak, a two 

 edged sword cleaving asunder the dark places of our ignorance. 

 By making use of a cultivation known to consist of typhoid bacilli, 

 we can distinguish the blood of those who have received a dose 

 of typhoid }xnson from the blood of others. 



Without further preamble let me describe the reaction as 

 you may see it to-night. Under the first microscope is a 

 " hanging drop " preparation of living typhoid bacilli to which 

 has been added a minute fraction of a drop of the blood of a 

 subject not suffering from typhoid. You will see it to contain 

 immense numbers of actively swimming rods. These will 

 continue swimming as you see them for many hours, until by 

 their multiplication the whole drop has become filled with single 

 rods. Under the second microscope is a similar preparation 

 except that the blood was derived from a patient suffering from 

 typhoid. In it the bacilli behave in a strikingly different way. 

 They appear benumbed or paralysed, the majority exhibit no 

 movements, others are spinning rapidly around on their own axes 

 like whirligigs or weathercocks, expending an immense amount of 

 energy but not getting forward. If you watch long enough 

 you will see many of the rods gathering into little groups or 

 clumps all over the preparation, like sheep huddling together 

 when frightened. Finally they cease from all movement, 

 and grow no longer as single free-swimming rods, but as 

 long motionless filaments, which interlace to form a netAVork, 

 and would be taken by an inexperienced observer for some 

 different organism altogether. 



Into the explanation of this remarkable reaction I do not 

 propose to enter. It is a difficult problem on which it would be 

 rash to theorise. But its practical value is easy to recognise. It 

 is possible by the examination of a single drop of blood, dried 



