PEOTEIN SKIN EEACTION 111 



4. Dilute acids and alkalis interfere with this 

 reaction. 



5. Sodium chloride interferes very slightly 

 with the reaction. 



6. Prolonging the time of heating makes the 

 reaction very much more delicate. 



THE PROTEIN SKIN REACTION. 



Much use has been made in recent years of 

 certain skin reactions for diagnostic purposes. 

 Such is the von Pirquet test in tuberculosis. I 

 have long held that this is a protein reaction. 

 The tubercular individual elaborates in his body 

 cells a ferment which splits up tuberculin and 

 sets the protein poison free, and the reaction is 

 due to the local effects of the liberated protein 

 poison on the epithelial cells. This explanation 

 is confirmed by recent observations. A man 

 claimed that he could not eat even a small 

 amount of any food containing nutmeg without 

 soon becoming sick and developing urticarial 

 rash. A bit of nutmeg was crushed in a mortar 

 in a few drops of sterile salt solution and a drop 

 of this suspension placed on the forearm and 

 scratched in with a von Pirquet scarafier. With- 

 in a few minutes a large wheal or hive developed 

 about the point. Similar tests have been made 

 with similar results on those sensitive to pep- 



