Abstract
I. Variola vaccine, when inoculated on the skin of sheep, produces vesicles, which take an intermediate form as they are found on the skin of calves and rabbits.
II. This form of vesicles is found on the sheep skin until 8th generation of successive transplanting, when the virulence seems suddenly impaired and in the 9th generation no vesicles can be prodnced, the only change on the skin being a desquamative inflammation of the smeared area. This continues until the 14th generation, when the virulence starts to recover itself again and reaches to its heights on the 23rd generation. After that no change was noticed until the last one (38th generation in the authors' experiment). For convenience sake the authors call the virus in these phases:
I stage of ovinization (1-8th generation)
II stage of ovinization (9-22nd generation)
III stage of ovinization (23rd generation and after)
III. Among these 54 sheep of the authors' expesiment not a single case of generalized reuption, severe general disturbances nor fatal case was encountered as they are described by Pissin as well as Fürstenberg. Just a remarkable raise in temperature was noticed in all animals.
IV. Linear inoculations of the original undiluted ovinized lymph on the calf skin produce typical vesicles up to the 8th generation (i. e. 1 stage of ovinization). The vesicles, however, become more and more atypically as the generations go on and after 11th transplantation no vesicles can be produced. This is also the case even with the lymph of the highest virulence (III stage of ovinization). That is to say, variola vaccine loses its virulence against calves with the complete adaptation to sheep body.
V. Inoculations on the shaven skin of rabbits with the 1:500 dilution of ovinized lymph of each generation until the 8th produce confluent or almost confluent vesicles. Further passage through sheep impairs the virulence of the lymph against rabbits, producing less or no vesicles but erythema on the rabbit skin, though the lymph attain the highest virulence against sheep. In another words, with the complete ovinization of variola vaccine by sheep passage the virulence of it against rabbits is almost lost.
VI. Ovinized lymph of the 20th generation was inoculated on two unvaccinated infants. Though ordinal variola vaccine, which was inoculated on the same individuals at the same time, produced typical vesicles no reaction was noticed with the ovinized lymph. This means that the ovinized lymph is avirulent also to human beings.
VII. In the early stages of sheep passage of variola vaccine it is immunogenic against the ordinal variola vaccine and never immuizing against inoculations with the ovinized veccine. With the progress of sheep passage, however, the immunizing property to the latter become more and more marked and the same to the former, on the contrary, decreases gradually, until it disappears altogether with the complete adaptation of the lymph to the sheep body, when the immunizing character of the lymph against the ovinized vaccine is perfectly developed.
VIII. Completely ovinized variola vaccine is highly immunizing against sheep-pox virus. But its practical application for the prevention of sheep-pox can not be relied upon, as it proved to be not potent enough for the immunization of animals.
IX. Sheep, which have recovered from sheep-pox infection, are not immune against ordinal variola vaccine. On the contrary, they are perfectly immune against ovinized variola vaccine, so that the latter seems very much more closely releted to sheep-pox virus in its characters.
