Spirometer invented by Dr. Dio Lewis, an early advocate of health through exercise and a gymnasium owner. Sold as a lung exerciser. Advertisement from 1898. From: http://www.amazon.com/1898-National-Spirometer-Gymnasium-Lewis/dp/images/B005DGYZMA
Spirometer invented by Dr. Dio Lewis, an early advocate of health through exercise and a gymnasium owner. Sold as a lung exerciser. Advertisement from 1898. From: http://www.amazon.com/1898-National-Spirometer-Gymnasium-Lewis/dp/images/B005DGYZMA