the extract dialyzed through a collodion membrane against distilled water at room temperature for 24 hours the water being changed every four hours the entire content of the dialysis tubes then is dried under vacuum at 65 u00b0 and the residual solids are ground to a fine powder with mortar and pestle an aqueous solution of proteinoid is produced by mixing 35 mg of the powder of example 1a per ml of water adjusting the ph to 7 4 with concentrated aqueous sodium bicarbonate and removing any insoluble materials by filtration one part by volume of this solids free solution of proteinoid then is rapidly injected into an equal volume of a freshly prepared 25 mg ml mixture of porcine insulin in ph 2 25 aqueous acetic acid the mixture which has a ph of approximately 3 5 is stirred in an ice bath for 15 minutes and filtered to separate the insulin bearing microspheres from the filtrate which is discarded after washing twice with ph 3 5 aqueous acetic acid the microspheres are resuspended in 10 parts by volume of ph 3 5 aqueous acetic acid microscopic examination of a portion of this suspension shows a high yield of microspheres which are predominantly between 0 5 and 5 0 microns in diameter and which dissolve rapidly when the suspension is neutralized to ph 7 4 by the addition of concentrated aqueous sodium bicarbonate the ph 3 5.