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The lapinized K vaccine was used to immunize 25 five-day-old pigs and 27 ten-day-old pigs. A group of 10 pigs were also included in the experiment as controls. All animals originated from eight sows treated with a lapinized K vaccine on the 70th day of pregnancy. On the 14th day following vaccination part of the pigs of the two test groups were revaccinated. Three months later half of the immunized pigs were infected with a pathogenic swine fever virus. The remaining animals were infected then in a six months time following immunization. Systematic clinical and morphological investigations were carried out. It was concluded that the 5-day-old animals possessed much lower immunologic responsiveness to the lapinized K vaccine against swine fever as against the 10-day-old ones. Revaccination with the same vaccine on the 14th day led to a weaker immune response as compared to single vaccination. The immunity of the vaccinated 10-day-old pigs, originating from sows that had been immunized with the same vaccine during pregnancy, lasted about three months.

Immunized were experimentally a total of 10 pigs with 2 cu. cm lapinized K vaccine and 10 cu. cm swine fever serum each. Reimmunization was performed a month later using only vaccine. After three and a half months the experimental pigs were included into the group of pigs producing serum against swine fever that were preliminary simultaneously immunized against hog cholera by the classical method. Swine fever antibodies in the serum of the experimental pigs showed a concentration that was equal to that in the serum of the regular donors as in both cases the serum titer ranged within the limits of 0.10 to 0.12 cu. cm per kilogram body weight. It is concluded that pigs intended for serum producers can be immunized with a lapinized K vaccine and serum against swine fever on the farms supplying the animals. After building up the basic immunity, which lasts about three and a half months the pigs could be bought over and included for serum production. Thus, the pathogenic hog cholera virus of the simultaneous immunization at the Institute (producer of serum) will be eliminated, economizing forage and labor and premises for several months, which are necessary for serum producing pigs.

Nonvaccinated pigs were infected with a pathogenic virus of swine fever in order to follow up the changes with some enzymes in their blood serum. It was found that there is a dependable rise in the values of the blood serum GOT (2.6.1. 1.) - From about 38 to approximately 108 mU per cu. cm; GPT (2. 6; 1.2.;-From about 12 up to 66 mU/cu. cm; LAP (3. 4. 1. 1)-from about 13 to 27 mU/cu. cm; and ALD (4. 1; 2. 7.) - from about 6 up to 19 mU/cu. cm. These changes were noticed as early as the 48th hour of infection, prior to the manifestation of the clinical symptoms of swine fever. They remained stable up to the end of the infection process. The activity of LDH (1. 1. 2. 7.) and amylase (3. 2. 1.1 .) was said to rise (not dependable statistically), and that of cholinesterase (3. 1 1. 8) - to drop gradually with the development of the infection process. The two phosphomonoesterases (3. 1. 3. 1 and 3. 1. 3. 2.) showed no essential changes. The changes taking place in the activity of these enzymes did not depend on the extent of the hemorrhagic diathesis characteristic of swine fever. So, this test, which has been unknown so far, is referred to as a characteristic paraclinical symptom of swine fever.