distilled water the fibers were next extracted with 10 volumes of 1 0m naoh for 24 hours at 25 u00b0 c in the presence of 1m na 2 so 4 under constant agitation the alkaline extracted collagen was then collected by filtration and neutralized with 0 1m hcl and the fibers collected washed to remove the residual salt and frozen an aliquot of the above purified fibers was first suspended in a 0 07m lactic acid solution the amount of fibers and the acid solution used was such that a 0 7 w v of collagen dispersion was reached the swollen fibers were then homogenized in a silverson homogenizer the dispersed collagen material thus obtained was filtered through a 40 u03bcm stainless steel mesh before it was ready for the implant fabrication a 500 ml of collagen dispersion was neutralized with 0 5 nh 4 oh to the isoelectric point about ph 5 to coacervate the fibers the coacervated fibers were partially dehydrated and molded into a circular mold and further dehydrated in the mold to obtain a matrix of a predetermined density the molded matrix was frozen and then subjected to a freeze drying procedure in a virtis freeze dryer virtis company inc gardiner n y.