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Ethicon LTD (Ethicon) restraining them from infringing Cyanamid’s letters patent1,043,518 The facts are set our in the opinion of Lord Dip lockAdrew J. Batespm QC and David Young for CyanamidSteph Gratwick QC and GD paterson fro EthiconTheir Lordships took time for consideration5 th February. The following opinions were deliveredLORD DIPLOCK. My lords this interlocutory appeal concerns a patent forpolymer known as a polyhydroxyacetic ester (PHAE). These are sutures a of akind that disintegrate and are absorbed by the human body once they haveserved their purpose. The appellants (Cyanamid) an American company are theregistered proprietors of the patent. Its priority date in the United Kingdom is 2 ndOctober 1964. At that date the absorbable sutures in use were of natural origin.There were made from animal tissues popularly known as catgut Therespondents (Ethicon) a subsidiary of another American company were thedominant suppliers of catgut sutures in the United Kingdom market.Cyanamid introduced their patented product in 1970. The chemical substance ofwhich it si made is a homopolymer, i.e. all the units in the chain except the firstand the last (the end stabilizers) consist of glycoside radices. Glycolide is theradical of glycolic acid, which is another name for hydroxyacetic. By 1973 thisproduct had succeed in capturing some 15 per cent of the United Kingdommarket for absorbable surgical sutures. Faced with this competition to catgut,Ethicon who supplied 80 per cent of the market were proposing to introduce theirown artificial suture (XLG). The chemical substance of which it si made is not ahomopolymer hut a copolymer, i.e. although 90 per cent by weight of the unitsin the chain consist of glycoside radicals, the remaining ten per cent are lactideradicals which are similar in chemical properties to glycoside radicals but notidentical in chemical composition.Cyanamid contend that XLG infringes their patent, of which the principal claim isA sterile article for the surgical repair or replacement of living tissue, the articlebeing readily absorbable by living tissue and being formed from apolyhydroxyacetic ester. As is disclosed in the body of the patent, neither thesubstance PHAE nor the method of making it into filaments was new at thepriority date. Processes for manufacturing filaments from PHAE had been thesubject of two earlier United StatesHL American Cyanamid v Ethicon (Lord Diplock 507300