Rosenow and Nickel's1 experiments on elective affinity are of great interest to the scientist, independently of the practical value of the results of those investigations. The practitioner, however, is interested in the practical application of the theory of focal infection; he wants to know whether the elimination of the foci of infection serves its purpose; whether vaccine therapy is efficacious ; whether it is proved that foci of infection are the cause of ocular diseases in most cases. Furthermore, he wants to know whether the results of the experiments are applicable to human beings, and can enlighten him in the treatment for ocular diseases.
THE LAW OF LARGE NUMBERS
It is up to the bacteriologist to decide whether experiments on several hundred rabbits and guinea-pigs are sufficient to make definite conclusions on the subject of elective affinity. Haden's and Rosenow and Nickel's experiments show that there are rabbits