Furthermore, the irregularities of the skull do not indicate local brain differences.
It is thought that the relative weight of the brain may be an indication of intellectual endowment, especially when the brain weight is compared with the weight of the rest of the body, and that culture in particular lines increases the surface of the cortex by deepening and multiplying the convolutions.

But these statements can not be applied off-hand to individuals, as the practise of phrenology would require.
_Defects of Memory--Amnesia._--The cases given just above, where the failure of speech was seen to be due to the loss of certain memories of words, illustrate also a series of mental defects, which are classed together as Amnesias.

Any failure in memory, except the normal lapses which we call forgetfulness, is included under this term.

Just as the loss of word memories occasions inability to speak, so that of other sorts of memories occasions other functional disturbances.

A patient may forget objects, and so not know how to use his penknife or to put on his shoes.