In this chapter, we learn that people are prone to various diseases, including physical frailty, fat duckling, young age, and so on. We also learn that some people are more susceptible to certain diseases than others, such as when they are young and healthy. In fact, we find out that some of the most common diseases are caused by people who are physically frail. For example, if you're a young person and you throw up a bunch of thorns on the exam, you'll get a lot of STDs. Or if you were a student and you eat too much and then throw up flowers, you might get some STDs as well. In other words, some people get sicker when they're young, while some people die from old age-related diseases. We learn that this is because some people have a tendency to get sick at a young age while others get sick later in life. So, for example, a young man who throws up lots of flowers on his exam might get a STD later on in life, while a young woman who eats too much might get STDs later on. This is just a sampling of the many STDs that we'll find out about in the next chapter.