There is however a real debateable ground between library and museum, with somewhat hazy boundaries which I believe that either is justified in overstepping whenever such an act supplies an omission and does not duplicate. In other words, there is a boundary region between library and museum that may be occupied by either, but should not be occupied by both. I shall try briefly to define this region and indicate how the library may occupy parts of it without legitimate criticism when the necessity arises. Descriptive and illustrative material is to be found in both library and museum. Speaking generally, the former is of primary importance in the library and the latter in the museum. Many books consist of descriptive text alone, without pictures or diagrams, and on the other hand a museum might contain specimens without labels, although they would not be of much use. In general, text with illustrations belongs in a library and specimens with labels in a museum. The mere statement of the distinction as it has just been given, however, shows that it may be very difficult to draw a line between the two kinds of collections. A museum has been defined as “a collection of good labels accompanied by illustrative specimens.” Here the value of the descriptive text is emphasized, even in the museum collection. When descriptive treatises are shelved in connection with the specimens, as in some modern museums, we have an expansion of the label into the book; and the museum, in this one particular at least, crosses the dividing line between it and the library. No one would blame it for so doing. Similarly the library may occasionally cross the line in the other direction without incurring blame. Let me repeat that both library and museum may contain descriptive and explanatory text and illustrative material. In the museum the text is usually in the form of labels, attached to the specimens, and these are generally material objects. In the library the text is in book form and the “specimens,” if we may so call them, are plates bound into the book. The first step taken by the library toward the line that separates it from the museum is when the plates, instead of being bound into a book, are kept separately in a portfolio. The accompanying text, corresponding to the “labels” of museum collections, may be on the same sheet as the plates (often on the reverse side) or on separate sheets, which may be bound into a book even when the plates are separate.