Abstract
This part of the present series of papers deals with the analytical observations of the course of the chick embryo passages and the fluctuations in the chick erythrocytes hemagglutination titre and the infectivity of the mumps viruses. Actually, 17 generations of the passages were observed over the period of 11 months (from Eebruary to January of the following year) . For the passages, amniotic fluid collected mainly from a single egg was utilized. The viruses were examined, qualitatively as well as quantitatively by means of the chick erythrocytes hemagglutination. The intervals of passages ranged from 6 days to 188 days. During these periods, the viruses were stored in the freezing compartment of an electric refrigerator. As reported in the earlier part of the same series of papers, 2 strains of virus, Showa B and Showa D, were isolated by the author and his co-workers. After the viruses became transferable, surplus amount of viruses were employed in various kinds of experiment. Namely, as the results of the human experimental mumps or other immunological studies, the passaged viruses mentioned in the above were presumed to have passaged as pure lines of the viruses. The viruses were first detected at the 4 th generation in one strain, and at the 5 th generation in another strain. For several gernrations (9 and 10 generations respectively) thereafter, uniform 100% infections was attained in the passages. After the 10 th generation, however, part of the inoculated eggs remained negative. Passages from such negative eggs were continued negative for several generations, but the results remained negative in all cases. In the passages during the month of November, an increases in the number of positive eggs was recorded. Furthermore, the increase in the hemagglutination titre was also noted. A remarkable example of the increase in the hemagglutination titre was recognized in the 9-10 th generations of Showa B strain, namely from 320 to 3840. Another example was recorded in Showa D strain in the 10-13 th generations, namely from 40 to 1280, 2560 and to 3840. When viewed from the whole course of the passages, a noteworthy fluctuation such as the appearance of positive eggs (the hemagglutination titre was 640) in the early stage of the passages, the diminution and regaining thereafter in the hemagglutination titre and the infectivity were observed. Although the present paper did not give any conclusion as to whether such fluctuations in the infectivity or in the adaptability to the host of mumps viruses can solely be attributed to the passages or to the environment (the temperature for storage ect.) as well, discussions were made in the present paper suggesting that the phenomenon observed is expressing the characteristics of mumps viruses under the influences of these two factors. At any rate, the increase and diminution in the so-called infectivity in the single regg passages were systematically observed over a long period of time.
