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.

Of the instruments for measuring the depth of colour of the blood, the
double pipette of Hoppe-Seyler is quite the most delicate. A solution of
carbonic oxide haemoglobin, accurately titrated, serves as the standard
of comparison. The reliable preparation and conservation of the normal
solution is however attended with such difficulties, that this method is
not clinically available. In the last few years, Langemeister, a pupil
of Kuehne's, has invented a method for colorimetric purposes, also
applicable to haemoglobin estimations. The instrument depends on the
principle, that from the thickness of the layer in which the solution to
be tested has the same colour intensity as a normal solution, the amount
of colour can be calculated. As a normal solution Langemeister uses a
glycerine solution of methaemoglobin prepared from pig's blood. To our
knowledge this method has not yet been applied clinically. Its
introduction would be valuable, for in practice we must at present be
content with methods that are less exact, in which c