Pic­tures Con­sid­ered #40 by Elio — In their pa­per writ­ten in 1930, two US De­part­ment of Agri­cul­ture sci­en­tists, L. A. Rogers and E. O. Whit­tier, prob­a­bly de­scribed the first con­tin­u­ous cul­ture de­vice for bac­te­ria. It had sev­eral of the fea­tures of what later be­came known as the chemo­stat: a growth cham­ber, a way to de­liver fresh nu­tri­ent at a set rate, a con­stant level de­vice (a side tube) to re­move spent medium at the same rate as that of ad­di­tion of fresh medium, and a sam­pling port.