SYPHILIS 



95 



The Wassermann Reaction. 



Since the last edition of this work appeared, the Wassermann 

 reaction has 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 containing the specific spirocheetes 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 hemolysis. This is used to 

 denote the liberation of hemoglobin 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 invisible. 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 acquire no power whatever over human 

 corpuscles. The power of hsemolyzing alien corpuscles is, there- 

 fore, a rare attribute of the serum of a normal animal, but can be 

 acquired by injecting the animal (" immunizing " it) with the 

 corpuscles it is desired to dissolve. 



