On the resulting page is the full set of limits. Journal Subset limits the search to particular groups of journals. Age Group is a very important set of limits because very few subject headings have an age group implied in the heading. Use this limit to restrict a search to a particular age group, such as geriatric populations. Limiting by age group automatically limits by human.
Animal is used to restrict the search to studies done on a specific animal.
Publication Type limits to documents of a specific type. Language limits to documents in that particular language. Human , Animal , Male , Female , Review Article , and Abstract limits are self-explanatory. This is NOT a good choice for most searches. The only people who should use this limit are those who run the same search every month.