To increase our understanding of biological systems, the first step is to make an observation at the level of organization that we wish to understand. It has yet to be conclusively shown that any laboratory animal has contracted emphysema solely as a result of exposure to cigarette smoke. Available mechanism-of-response studies at the tissue, cellular, or biochemical level of organization are not useful in elucidating the relationship between emphysema and exposure to cigarette smoke without an animal model for the disease VSports手机版. If progress in understanding the etiology of emphysema from cigarette smoking is judged to be important to the scientific and regulatory communities, the highest priority should be given to discovering a suitable animal model. .