Final answer:
Human blood is no longer used in the preparation of culture media due to contamination risks, ethical concerns, and lack of essential nutrients. Instead, artificial media are used.
Step-by-step explanation:
Human blood is no longer used in the preparation of culture media due to several reasons. Firstly, human blood can be contaminated with viruses, which can pose a risk to researchers working in the lab. Secondly, using human blood raises ethical concerns and may not be socially acceptable. Thirdly, blood lacks essential nutrients that are necessary for bacterial growth. Instead, culture media are now developed artificially by mixing appropriate nutrients and chemicals to provide an equivalent environment for culturing bacteria and viruses.