Biodegradable polymer which, edible films have gained more attention due to their environmentally-friendly characteristics, vast variety and availability, non-toxicity, and low cost. Biodegradable polymers have a long history, and since many are natural products, the precise timeline of their discovery and use cannot be accurately traced. One of the first medicinal uses of a biodegradable polymer was the catgut suture, which dates back to at least 100 AD. The first catgut sutures were made from the intestines of sheep, but modern catgut sutures are made from purified collagen extracted from the small intestines of cattle, sheep, or goats. The concept of synthetic
Musical instrument classification that are rhythmic, a scheme which was probably the first scholarly attempt, while the earlier ones were traditional, folk taxonomies. More usually, instruments are classified according to how the sound is initially produced (regardless of post-processing, i.e., an electric guitar is still a string-instrument regardless of what analog or digital/computational post-processing effects pedals may be used with it). The modern system divides instruments into wind, strings and percussion. It is of Greek origin (in the Hellenistic period, prominent proponents being Nicomachus and Porphyry). The scheme was later expanded by Martin Agricola, who distinguished plucked string instruments, such as guitars, from