Humans are afflicted with the mania of having or possessing things. The chapter in question is a poem titled Animals. It was composed by American poet Walt Whitman. The poem makes comparisons between people and animals. /span> According to the Oxford English Dictionary, mania is "a severe mental disorder characterised by abnormal intense emotions that usually involve an excessive need for change or excitement." This disease affects how a person thinks and acts. Manic depression is a term used to describe the interaction of bipolar disorder and substance abuse. Bipolar disorder is a mental illness that causes periods of extreme moodiness or depression. There are different types of bipolar disorders, such as bipolar I disorder and bipolar II disorder. Manic depression is a part of bipolar I disorder. People who suffer from manic depression experience episodes of extreme joy or elation followed by severe depression. During these episodes, their ability to function normally is impaired, and they are at risk for harming themselves or others. The word "maniac" comes from the Greek manikos, which means "of the vine," because insanity was once believed to be caused by a demon that possessed your body through contact with your food. In modern usage, the word refers to someone who is extremely crazy or insane. People with mania tend to spend more than normal during periods of elevated mood.