The Vatican Collections 
19 
moreover, to the fallibility of all indexes, that it is impossible to list all the 
relationships of a particular document. Here only the simplest are given, 
such as names of persons or places cited in the preamble. It is obvious, then, 
that these series can not be used with the idea of exhausting the material on 
any subject. On the other hand the positive information given is often sug¬ 
gestive and important, though references are often hard to trace and are 
sometimes lacking. Those bearing upon the subject are given in the Ap¬ 
pendix. 
The remaining volumes of indexes are of the most varied utility. Some 
refer to collections which have disappeared or are dispersed, in some cases 
the method of reference has been changed, many are too inaccurate to trust. 
On the whole, however, most of the indici have some interest, if their value 
be slight. There are in addition inventories and indexes in the archivist’s 
room which are not mentioned in the Inventorium Indicum, others which are 
listed with collections; and many volumes contain individual apparatus of 
some kind. All such aids as seem useful, will be noted in connection with the 
series to which they apply. 
One has no surety that by examining the indici one has exhausted the 
archives. As will be seen from the following special studies, many of the 
most important collections are entirely without such guide, and probably no 
one person is aware just how many such series exist hidden, or rather not 
yet brought to light. 
