Numbers
The most common method of enumerating is that of the finger count. The usual method is to count the fingers, beginning with the little finger of the right hand, in succession touching each finger with the forefinger of the other hand. The count of the thumb, li′-ma, five, is one of the words for hand. The sixth count begins with the little finger of the left hand, and the tenth reaches the thumb. The eleventh count begins with the little finger of the right hand again, and so the count continues. The Igorot system is evidently decimal. One man, however, invariably recorded his eleventh count on his toes, from which he returned to the little finger of his right hand for the twenty-first count.
A common method of enumerating is one in which the record is kept with small pebbles placed together one after another on the ground.
Another method in frequent use preserves the record in the number of sections of a slender twig which is bent or broken half across for each count.
When an Igorot works for an American he records each day by a notch in a small stick. A very neat record for the month was made by one of our servants who prepared a three-sided stick less than 2 inches long. Day by day he cut notches in this stick, ten on each edge.
When a record is wanted for a long time—as when one man loans another money for a year or more—he ties a knot in a string for each peso loaned.
The Igorot subtracts by addition. He counts forward in the total of fingers or pebbles the number he wishes to subtract, and then he again counts the remainder forward.
Lineal measure
The distance between the tips of the thumb and middle finger extended and opposed is the shortest linear measure used by the Igorot, although he may measure by eye with more detail and exactness, as when he notes half the above distance. This span measure is called “chang′-an” or “i′-sa chang′-an,” “chu′-wa chang′-an,” etc.