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People's bottoms are getting so big that injections into them are becoming ineffective, a study in Ireland has shown. Many are now so obese that commonly used needles are simply not long enough to penetrate the fat and reach the muscle, where they are aimed, Victoria Chan told the annual meeting of the Radiological Society of America in Chicago. Dr Chan's study shows that 68% of “intramuscular” injections in the buttocks do not reach the muscle. “The amount of fat tissue overlying the muscles exceeds the length of the needles commonly used for these injections,” she said. Researchers injected 50 patients and included a small air bubble in the injection, which was then located by computed tomography scans. The team also measured body mass index, distance to injection site, and thickness of fat and muscle. Overall, the success rate of the injections was only 32%. More than half (56%) of the injections in men reached the muscle, but in women it was 8% (www.timesonline.co.uk).

Is breast cancer a zoonosis? In mice, breast cancer is commonly caused by mouse mammary tumour virus, which is transmitted in the germline and through infectious virions. The existence of a human homologue of …