Abstract
Of 341 mated female mice observed during a 2-year period, 29 died. 12 of these were examined in detail: 1 had leukaemia; 2 had renal lesions; 6 had intussusception of colon; 5 had liver necrosis. Of the 6 with intussusception, 5 had an infestation of a nematode, Aspiculuris tetraptera, in the colon: 2 mice with no intussusception were also infested.