in vivo, in vitro, ex vivo

These three latin terms are used in various ways by scientists. However, in biology "in vivo" is used to mean "in a living organism". In other words, all we need to do in supply food and water and the organism is self-sustaining.

Neuroscientists use the term this way. Thus, in vivo experiments will involve entire breathing animals. These are most often worms, zebra fish, fruit flies, mice and rats. Aplysia was a very useful animal in past, but is not much used these days.

Living brain cells isolated from these animals are not self-sustaining, thus are normally called "in vitro" by neuroscientists. This is because we need to supply oxygen and sugars, and this is done in a glass container. Hardly ever are they referred to as "ex vivo". A survey of the two leading neuroscience journals, Neuron and Nature Neuroscience proves this point. Pubmed searches of the text words "in vitro" and "ex vivo" show that the former term is used in 50-fold more articles.