Since Pasteur in 1885 gave to the world his method of treating rabies by subcutaneous injection of fixed virus prepared from the spinal cord of inoculated rabbits by the process of drying, a number of other methods have been suggested and tested in a practical way. All, however, must be considered as modifications of the method of Pasteur and are based on the fundamental principles which he first discovered.
Chief among these modifications may be mentioned that of Högyes, who, instead of using the dried cord, begins with injections of a highly diluted virus and gradually increases the concentration until immunity is established. The Babes-Puscariu method is based on the fact pointed out first by Babes and later by Puscariu that the virulence of the cord is diminished by heat and the loss of virulence is proportional to the time of exposure. The same effect may be produced by heating