Il8 CLINICAL BACTERIOLOGY AND -H/RMATOLOGY 



fact practice is an essential in the diagnosis of syphilis by 

 the recognition of the spirochsete, and the practitioner is 

 recommended to identify the organism as often as he can in 

 undoubted cases before attempting its recognition in doubt- 

 ful ones for diagnostic purposes. 



THE WASSERMANN REACTION. 



The Wassermann reaction has now attained enormous 

 importance in the diagnosis of syphilis. It supplies one of 

 the great desiderata of medicine, a blood test that is highly 

 trustworthy and that can be applied when no material con- 

 taining the specific spirochaetes is available for examination. 

 The theory of the reaction is somewhat complicated, and not 

 easily understood by those who have not followed the recent 

 work in the subject of immunity, but it will be described, as it 

 is essential for the comprehension of the reaction. 



Let us first understand the term k&molysis. This is used 

 to denote the liberation of haemoglobin from the red blood- 

 corpuscles. If the latter are mixed with an inert solution, 

 such as normal saline, and allowed to stand, they settle slowly, 

 forming ultimately a red deposit in a clear and colourless 

 fluid. But if certain substances are present the haemoglobin 

 is set free and colours the liquid red, and there is practically 

 no deposit, the stromata of the corpuscles being almost in- 

 visible. Many agents will- accomplish this haemolysis, but for 

 our purposes we need only consider the haemolysins of serum. 

 Occasionally the normal serum of one animal will haemolyze 

 the corpuscles of another species ; thus, if fresh human serum 

 be incubated with the red corpuscles of a sheep, the latter will 

 frequently be dissolved. As a rule, however, the serum of a 

 normal animal has no action, but it can be made to acquire 

 such haemolytic properties as we have described by injecting 

 the animal with the corpuscles from an animal of the second 

 species. For example, a normal rabbit's serum is devoid of 

 action on human red corpuscles; but if the rabbit be injected 

 with two or three doses of human red corpuscles at intervals 

 of a week or so, it will acquire new properties, and if now 

 some of its serum be mixed with human red corpuscles and 

 incubated, haemolysis will occur. Similarly, a normal rabbit's 

 serum will not dissolve sheep's corpuscles, but if the animal 

 be injected with sheep's corpuscles, it will do so, but will 



