However valuable the knowledge of the absolute number may be for a judgment on the course of the illness, it gives us no information about the AMOUNT OF HAEMOGLOBIN IN THE BLOOD, which is the decisive measure of the degree of the anaemia. A number of clinical methods are in use for this estimation; first direct, such as the colorimetric estimation of the amount of haemoglobin, secondly indirect, such as the determination of the specific gravity or of the volume of the red corpuscles, and perhaps also the estimation of the dry substance of the total blood. Among the direct methods for haemoglobin estimation, which aim at the measurement of the depth of colour of the blood, we wish first to mention one, which though it lays no claim to great clinical accuracy has often done us good service as a rapid indicator at the bedside. A little blood is caught on a piece of linen or filter-paper, and allowed to distribute itself in a thin layer. In this manner one can recognise the difference between the colour of anaemic and of healthy blood more clearly than in the drop as it comes from the finger prick. After a few trials one can in this way draw conclusions as to the degree of the existing anaemia. Could this simple method which is so convenient, which can be carried out at the time of consultation, come more into vogue, it alone would contribute to the decline of the favourite stop-gap diagnosis, 'anaemia.' For neurasthenic patients also, who so often fancy themselves anaemic and in addition look so, a _demonstratio ad oculos_ such as this is often sufficient to persuade them of the contrary.