The mechanism underlying the vascular action of endotoxin has been intensively studied with controversial results (1). Evidence has been presented that endotoxin may exert a direct effect on the vessel wall. On the other hand, it m a y act by releasing or potentiating vasoacfive substances, or its peripheral effects may be secondary to alterations in cardiac output and plasma volume. To investigate possible direct vascular actions of endotoxin, the isolated, perfused rat liver offers some unique advantages. A well established technique of perfusion is available and the isolated oxygenated liver maintains its metabolic and histological integrity for a period of 4 to 5 hours. Moreover, this preparation allows for direct, precise measurements of hepatic blood flow, and permits controlled alteration of the perfusing media. By the very nature of the system, endotoxin effects on liver circulation that are secondary to changes in the cardiac output are eliminated. Most important, minor and transient hemodynamic effects of bacterial lipopolysaccharide can be studied at concentrations far below the lethal doses used in the majority of studies in intact animals. Materials and MethodsAnimals.--Adult male Sprague-Dawley rats were used as both blood and liver donors. All animals weighed between 450 and 550 gin and were allowed water and Purina lab chow ad libitum until the time of sacrifice. Donor blood was obtained immediately prior to use in heparinized vacutainer tubes by aortic puncture of etherized rats.Perfusion Technfilue.--The procedure used for the removal and perfusion of a rat liver is essentially that described in detail by Miller (2, 3). The technique involves rapidly removing the liver from an animal and placing it in a system where it is perfused by oxygenated, heparinized blood at 37°C. To insure sterility, all glassware and tubing were autoclaved and assembled in an aseptic manner, and the operative procedure was carried out aseptically on a surgicall~r prepared and draped rat, using sterile equipment. Sterility was monitored throughout the experiments to be described by random culture of the perfusate at various time intervals. Samples plated on blood agar and incubated at 37°C uniformly showed no growth.

Streptococcus suis was recovered from 9 outbreaks of septicaemia and meningitis in weaned pigs between 1979 and 1983. Fifteen isolates from 7 outbreaks were identified as S. suis type 9, and 3 isolates from 2 outbreaks as S. suis type 2. Three further isolates of S. suis type 2 and an isolate of S. suis type 3 were recovered from cases of bronchopneumonia in weaned pigs from 4 other piggeries.

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