260 MICROBES AND TOXINS 



The reaction is also of value in the distinction between 

 general paralysis and other mental affections which bear an 

 external resemblance to it, among others from dementia praecox. 

 Bordet's reaction has also been applied in the diagnosis of 

 hydatid cysts due to the echinococcus. 



Also it has been employed in the detection of blood and 

 foreign proteins for which it is an even more sensitive test than 

 precipitation : it requires, however, such delicate manipulation, 

 and is so extremely sensitive, that it can hardly be trusted in 

 certain cases; according to Friedberger it is capable of 

 detecting the minute trace of protein present in human per- 

 spiration, so that the hands of the experimenter himself may 

 introduce an error. 



It has been employed in the differentiation of different races 

 of man and of monkeys : not that the distinction between man 

 and monkeys is so absolutely necessary as to show the sort of 

 hierarchy which exists. Man is as far removed from the orang 

 as the orang is from the macacus ; however, man is more nearly 

 related to the orang than the latter is to certain species of 

 macacus. It is even possible, it is said, to distinguish by sero- 

 diagnosis an individual of Mongolian race from a Malay. 



The biological reactions thus are of value, not only in the 

 physiology of immunity and of nutrition, but even in zoology 

 and anthropology. 



Tuberculin Tests. 



A dose of tuberculin which produces no effect in a healthy 

 subject may determine in a tuberculous individual a definite 

 reaction, consisting of general and local phenomena, fever, 

 inflammation, and oedema round the tubercles and at the site 

 of injection. 



It was long thought that the reaction only took place in the 

 neighbourhood of the tuberculous lesions themselves, and 

 consisted in the inflammation and destruction of a certain 

 number of cells, the fever being due to the absorption of the 

 cellular debris. Von Pirquet, however, discovered that the 

 skin of a tuberculous patient reacts to tuberculin at every point, 



