Hammond et al (17) exposed 89 male “pedigree”
beagle dogs to cigarette smoke via tracheostomy, with a further
8 animals receiving tracheostomy but no smoke. The
aim of this work was to determine whether “dogs smoking
cigarettes equipped with ef cient lters would develop pulmonary
emphysema and brosis to a greater degree, if at all,
than dogs smoking the same number of non lter cigarettes”
(pulmonary neoplasia was not a planned endpoint). The un-
ltered cigarettes used produced 35 mg of tar and 1.85 mg of
nicotine; the lter cigarettes had yields approximately half
this amount. Animals were “habituated to smoke” over a
56-day period, using cigarettes with lters. After this period
animals were exposed to smoke twice daily for up to
875 days. The following groups were used: F: lter cigarette,
7 cigarettes/day, 17 mg tar/cigarette, 12 animals; L: non-
lter cigarette, 3.5 cigarettes/day, 35 mg/cigarette, 12 animals;
and H: non lter, 7 cigarettes/day, 35 mg/cigarette,
24 animals. Group h was a replicate of Group H, where the
38 animals were used “for a preliminary long-term experiment
on the effects of smoking non lter cigarettes” (see
later).he inhalation techniques usually consisted of a mask over the nose of the animal