A system of staple cartridges, comprising: a first staple cartridge, comprising: a first cartridge body; and first staples removably stored in said first cartridge body, wherein said first staples are comprised of a first alloy, and wherein said first staples are configured to fracture after being implanted in a patient; and a second staple cartridge, comprising: a second cartridge body; and second staples removably stored in said second cartridge body, wherein said second staples are comprised of a titanium alloy, wherein said second staples are configured to fracture after being implanted in a patient, and wherein said second staples are stiffer than said first staples, wherein either i) the first alloy is a magnesium alloy and said first staples are configured to fracture within 30 days after being implanted in a patient, and said second staples are configured to fracture after 30 days after being implanted in a patient; or ii) said first staples are configured to fracture within 100 days after being implanted in a patient, and said second staples are configured to fracture after 100 days after being implanted in a patient. a first staple cartridge, comprising: a first cartridge body; and first staples removably stored in said first cartridge body, wherein said first staples are comprised of a first alloy, and wherein said first staples are configured to fracture after being implanted in a patient; and a first cartridge body; and first staples removably stored in said first cartridge body, wherein said first staples are comprised of a first alloy, and wherein said first staples are configured to fracture after being implanted in a patient; and a second staple cartridge, comprising: a second cartridge body; and second staples removably stored in said second cartridge body, wherein said second staples are comprised of a titanium alloy, wherein said second staples are configured to fracture after being implanted in a patient, and wherein said second staples are stiffer than said first staples, wherein either i) the first alloy is a magnesium alloy and said first staples are configured to fracture within 30 days after being implanted in a patient, and said second staples are configured to fracture after 30 days after being implanted in a patient; or ii) said first staples are configured to fracture within 100 days after being implanted in a patient, and said second staples are configured to fracture after 100 days after being implanted in a patient. a second cartridge body; and second staples removably stored in said second cartridge body, wherein said second staples are comprised of a titanium alloy, wherein said second staples are configured to fracture after being implanted in a patient, and wherein said second staples are stiffer than said first staples, wherein either i) the first alloy is a magnesium alloy and said first staples are configured to fracture within 30 days after being implanted in a patient, and said second staples are configured to fracture after 30 days after being implanted in a patient; or ii) said first staples are configured to fracture within 100 days after being implanted in a patient, and said second staples are configured to fracture after 100 days after being implanted in a patient. i) the first alloy is a magnesium alloy and said first staples are configured to fracture within 30 days after being implanted in a patient, and said second staples are configured to fracture after 30 days after being implanted in a patient; or ii) said first staples are configured to fracture within 100 days after being implanted in a patient, and said second staples are configured to fracture after 100 days after being implanted in a patient.