In the rabbit intestine Peyer’s patches can easily be distinguished. They are found in the jejunum and ileum, but not in the duodenum. The highest number observed is seven. In most animals the first, i.e. proximally situated patch has a rather well-defined place in the beginning of the jejunum; similarly, the last, i.e. distally situated one mostly has its place in the end of the ileum. The demarcation of the three classical sections of the small intestine is discussed from a comparative viewpoint with special criticism as to what is called ileum in ma