[Possible inspiratory or expiratory synergism between various external and internal intercostal muscles in cats].

The electrical activities of the lateral parts of the external and internal intercostal muscles were recorded in decerebrated cats during eupnea and in the course of artificially induced dyspnoea, elicited in order to reinforce the inspiratory or expiratory central drive. Our results indicate that in the cephalic spaces (1st to 5th rib), external and internal intercostals are synergists during inspiration. In the caudal spaces (9th to 13th rib), the same muscles are activated during expiration only. In the intermediate part of the thorax (5th to 9th rib), external intercostals are inspiratory muscles, internal intercostals are expiratory muscles.