1. The mechanical properties of the lungs of five symptom-free asthmatic subjects and two normal subjects were measured before and during provocation with nebulized methacholine.

2. Before provocation abnormalities of some aspects of the mechanical function of the lungs were found in four of the asthmatic subjects.

3. Pulmonary resistance increased within one breath of the methacholine inhalation and was the measurement of lung function which changed most in response to methacholine in both asthmatic and normal subjects. However, asthmatic subjects had a much greater response than normal subjects.

4. The results of the study suggest that both the large and the small airways respond to provocation with methacholine. The larger airways appear to respond faster than the smaller airways and the response of the smaller airways appears to be more prolonged.

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