At the onset of an epidemic in a closed institution about one-fourth of the inmates were skin-tested. During the year following the skin test, 5 cases of hepatitis with jaundice were recorded among 320 skin-tested individuals with unknown histories, one in the 144 skin test-positive, and 4 in the 176 skin test-negative subjects. In contrast 112 cases occurred among the 825 non-skin-tested individuals. Thus, the incidence of jaundice in the skin-tested group was 1.6 per cent as against 13.6 per cent in the non-skin-tested individuals. Possible explanations for this observation have been discussed.

The effect of various antimicrobial agents, such as aureomycin, terramycin, streptomycin, chloromycetin, penicillin, polymyxin, and sulfaguanidine on the development of massive dietary necrosis of the liver in rats has been studied. Delay in the production of hepatic necrosis was obtained from aureomycin and, to a lesser extent, from terramycin and streptomycin. Indication of temporary protection was shown by sulfaguanidine, whereas chloromycetin, polymyxin, and penicillin were not protective. B 12 , added alone, or in combination with aureomycin, to the basal experimental diet had no influence on the development of hepatic necrosis. A combination of pectin with streptomycin enhanced the protective effect of the antibiotic. All the antimicrobial agents tested, without relation to their effect on hepatic necrosis, produced temporary stimulation of growth in the experimental animals. The beneficial effect of aureomycin was not limited to the delay of hepatic necrosis but manifested itself also in the prevention of hepatic cirrhosis in rats fed a low protein (casein)-high fat diet. In contrast to control animals showing the usual combination of cirrhosis and renal changes, the rats receiving supplements of aureomycin were free of both cirrhosis and renal changes. The rats receiving aureomycin took more food in and gained weight. No microscopic alterations were seen in the pancreas of the control rats with cirrhosis. In both groups of experiments (necrosis and cirrhosis) the antimicrobial agents, with the exception of penicillin, were given mixed with the food. Their possible effect on the intestinal flora is discussed.

Two viral agents have been procured from patients with infectious hepatitisin two widely separated outbreaks of the disease by transfer of acute stage serum and stool filtrates to and passage in tissue cultures of rabbit liver cells in roller tubes and minced chick embryos in Simms-Sanders medium followed by passage in the amniotic cavity of the chick. Cultures of both agents, designated the Akiba and NL strains of virus, induced mild hepatitis without jaundice in the majority of volunteers tested after an incubation period of from 9 to 38 days. Although these agents have not been identified definitely as the virus of infectious hepatitis, the available evidence, as discussed, is compatible with the suggestion that such they are.

The successful cultivation of the virus of infectious hepatitis in chick embryo tissue culture and in the amniotic cavity of the embryonated hen's egg is supported by a comparison of the disease induced in volunteers by the cultivated virus with hepatitis without jaundice resulting from experimental infection with natural infectious hepatitis virus. Both types of viral preparations produced illnesses in comparable percentages of volunteers (83 and 75 per cent, respectively) after similar average periods of incubation (24.4 and 23.4 days, respectively) and of similar average duration (28.3 and 27.6 days, respectively). The disease could be divided in both groups of patients into a primary stage, followed after a short interval of relative well being by the secondary stage. The illnesses in both instances were characterized by anorexia, nausea, vomiting, enlarged, tender livers and abnormal liver function tests, and frequently temperature elevations. They differed in that jaundice was observed in 31 per cent of the cases resulting from infection with natural virus but not in any patients infected with the cultivated virus.

The results observed after experimental inoculation of active mumps virus into 41 vaccinated and 32 unvaccinated children,—with the consent of their parents or guardians,—indicated that formol-inactivated mumps virus obtained from the parotid gland of the infected monkey and employed as a vaccine in the manner which has been described increased the resistance of about half of those to whom it was administered.

Of 163 persons giving positive complement fixation tests who were exposed to mumps, 1 afterwards developed the disease; of 285 negative reactors similarly exposed, 56 afterwards came down with mumps. Of 78 individuals subjected to intimate exposure to mumps whose tests were originally negative and who failed to develop the disease, 41 per cent gave positive reactions when tested 1 month later. Seventy-seven per cent of complement fixation tests done on the sera of 565 normal adults who admitted a previous attack of mumps were positive. A similar correlation was recorded in tests on the sera of a small group of children with positive histories. Of 356 medical students admitting previous attacks, 80 per cent gave positive tests. Of 386 normal adults who denied previous attacks, 42 per cent gave positive tests; of 85 children giving negative histories, 38 per cent reacted positively. The results of complement fixation tests on the sera of 1665 normal adults (over 17 years) and 679 children (1 to 17 years) are recorded. It has been shown that 63 per cent of the adults and 57 per cent of the children had antibody in their blood which reacted with the virus of mumps. In groups in which exceptionally intense exposure was not known to have occurred in the past, the proportions of positive reactors were: adults, 61 per cent; children, 49 per cent. In contrast to these normal persons, the incidence of positive reactors among permanently institutionalized mental defectives was 38 per cent of 356 adults and 32 per cent of 475 children. In only 2 per cent of 320 normal adults and children did the titer of complement-fixing antibody reach 1–192. In no instance in which the endpoint was determined was a higher titer recorded. The results of complement fixation tests on the sera of mother and newborn infant were essentially the same in 5 instances.

The results of skin tests read at 48 hours on several hundred adults and children in which heat-inactivated mumps virus was the antigen have been presented and discussed. They can be summarized as follows:— Of 89 persons tested before the onset of mumps, 89 per cent exhibited erythematous reactions 10 mm. or less in diameter and 95 per cent, reactions 15 mm. or less in diameter. Of 40 persons tested during the first 5 days of mumps, 95 per cent exhibited reactions 10 mm. or less and 98 per cent reactions 15 mm. or less. Of 480 exposed persons the attack rate of mumps was 46 per cent among 340 with reactions 10 mm. or less and 10 per cent among 240 with reactions greater than 10 mm. The attack rate was only 2 per cent among 161 with reactions exceeding 15 mm. The attack rates in 13 skin-tested groups which were exposed to mumps tended to be inversely proportional to the incidence of reactions exceeding 10 mm. The incidence of reactions exceeding 10 mm. was approximately twice as high among 529 adults (persons 18 years or older) as it was among 306 children (persons under 18 years). Of 179 adults giving positive histories of mumps, 82 per cent exhibited skin reactions exceeding 10 mm. In certain groups the correlation between history and positive skin test was as high as 0.9. Of 132 adults giving negative histories, 58 per cent exhibited skin reactions of this magnitude. The proportion of reactions exceeding 10 mm. in a small number of children giving positive histories was 75 per cent. The proportion of reactions less than 10 mm. was 15 per cent. Of 167 adults with positive complement fixation tests, 87 per cent exhibited skin reactions exceeding 10 mm. Of 111 adults with negative complement fixation tests, 52 per cent exhibited reactions exceeding 10 mm. Of 43 children with positive complement fixation tests, the skin test reactions exceeded 10 mm. in 70 per cent. The skin reactions exceeded 10 mm. in 29 per cent of 105 children with negative complement fixation tests. In 69 of 72 individuals in whom skin reactions exceeded 10 mm., complement-fixing antibody either appeared in the blood or increased in amount within about 2 weeks after the tests were done. Such antibody responses likewise were observed in 34 of 76 individuals in whom skin reactions were 10 mm. or less. The data summarized up to this point were obtained with virus derived from the infected parotid gland of monkeys. The results of simultaneous tests in 82 individuals employing materials prepared from infected monkey parotid gland and amniotic membrane of chick embryos infected with mumps virus indicated in general that the same individual responded in a similar manner to both antigens. In many instances, however, the membrane material produced weaker reactions. Occasionally an individual failed to react at all to one of these materials but did respond to the other.