Abstract
1. Calves subjected to a natural infection proved to be immune against subcutaneous inoculation of virulent blood carried out 20-34 days after their recovery. To determine the duration of the immunity produced by the natural infection further investigations are necessary.
2. Subcutaneous inoculation of blood, saliva, vesicular content, and emulsion of spleen and lymphatic gland from an infected animal produced the disease in the calves experimented on. The minimum dose of virulent blood for a calf was 2c.c.
3. The blood-serum taken from the animal recovered from one attack of this disease was found to have a protective action which can be intensified by repeated injections of the virulent blood (100, 500, 1000c.c.)
4. The period of incubation in this disease is sometimes as short as 24 hours. To test, therefore, the protective action of an immune serum, injection of serum first and of virus one or two days later is preferable to the injection of both at the same time.
5. The animals treated with the immune serum in a dose of 0, 53c.c. per kilo body-weight proved to be immune against injection of 10c.c. of virulent blood carried out 3 weeks later. To determine the relation between the dose of serum and the duration of immunity further investigations are necessary.
