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PLATES XXIII AND XXIVP R O B L E M S of husbandry, including management and costs, have always caused difficulties in the use of cows for the study of bovine mastitis. Goats and sheep have been used as a substitute, but with these species husbandry problems are also considerable. A laboratory animal model for studying mastitis that was inexpensive and readily maintained by laboratories with standard facilities would be of considerable importance. This paper describes the production of experimental mastitis in mice by intramamniary inoculation. Organisms that are commonly associated with naturally occurring bovine mastitis were inoculated and the macroscopic and histological responses observed closely resembled those that occur in the cow. The model provides a convenient system for fundamental studies and quantitative experiments on mastitis prior to final assessment in cattle. MATERIALS AND METHODSMice. The BSVS strain, maintained as a closed colony at this Institute for several years, was used. In preliminary experiments mice that had produced more than one litter and were at varying stages of lactation were taken from the breeding stock. In later experiments mice that had borne only one litter and were at the 10th-15th day of lactation were used to provide a more constant standard. Offspring were removed from the lactating mice and disposed of about 1-2 hr before inoculation.Bacteria inoculated. The following bacterial species were used in infection experiments : Staphylococcus aureus (strain S57), Streptococcus agalactiae (strains S 13 and 122), Corynebacterium pyogenes (strain PM l), Escherichia coli (strain GS. 1) and Pseudomonas aeruginosa (strain GS. 2). All these strains had originally been isolated from cases of bovine mastitis.Inocula were prepared from cultures in Todd-Hewitt broth (C. pyogenes in serum broth) and the bacterial suspensions were standardised to Brown's tube no. 8 before further dilution. Bacterial counts were made by the method of Miles and Misra (Miles, Misra and Irwin, 1938). Control inocula consisted of heat-killed organisms, culture filtrate and culture media. The volume inoculated was approximately 0.05 ml per teat.The mice were lightly anaesthetised with ether and were laid on their backs and to one side on a small cork board so as to present the teats chosen for inoculation ( fig. 1). The teats were lightly dabbed with cotton-wool soaked in surgical spirit; this laid down the hair around the teats and facilitated subsequent observation. Hamilton 33G steel needles (V. A. Howe Ltd, Pembridge Road, London),(1 cm) long with Luer fitting and mounted on 1-ml disposable plastic syringes were employed. During inoculation each teat was viewed through a x 10 bench binocular magnifier (Vickers " Sterimag "). The flaccid teat was held lightly with fine forceps near its tip and the needle positioned at the centre of the tip of the teat; the needle was then Intramammary inoculation technique.

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Abstract. Gnotobiotic piglets were infected with a strain of rotavirus that had been isolated from a calf and passaged four times in piglets. The resulting disease was studied by light and electron microscopy at 21,44 and 68h after inoculation. In thesmall intestine infection caused desquamation of the epithelial cells of the villi resulting in severe stunting. There was severe damage to microvilli and accumulation of lipid within the cytoplasm. Virus particles were seen in epithelial cells covering the stunted villi. Infection also caused desquamation of the superficial epithelial cells of the stomach mucosa and of the epithelial cells of the bronchi, bronchioles, and alveoli of the lungs. The reovirus-like particles, which have been seen in faeces of young children with acute nonbacterial gastroenteritis, have been found to be morphologically indistinguishable from those of neonatal calf diarrhoea [8, 101. The calf and human viruses also appeared morphologically and antigenically distinct from both reoviruses and orbiviruses, and the term rotavirus has been proposed [7-91.Although the calf and human rotaviruses are morphologically indistinguishable, we were unable to infect calves with human virus. Piglets, however, are susceptible to infection with human virus [5] but do not become ill. We passed calf rotavirus serially five times in gnotobiotic piglets, and each passage produced profuse diarrhoea, depression and anorexia. Our serological studies have shown that pigs are naturally infected either with calf

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