BROOKES, ON MICROSCOPES AT THE EXHIBITION. 87 
Messrs. Smith, Beck, and Beck, are extremely beautiful and in- 
structive. 
The works of individual exhibitors, in the British and Foreign 
departments respectively, will now be briefly noticed. 
British Haehibitors. 
C. Baxer, H.M. (United Kingdom, 2853), exhibits a creditable 
collection of well-constructed microscopes, the prices of which 
are moderate. The stands are after Mr. Ross’s model. The 
objectives are of very fair quality for general purposes; some of 
the low powers are very good. His students’ microscopes are 
well and economically constructed. 
Professor Brann, M. (United Kingdom, 2855), has devised and 
exhibited an exceedingly simple and convenient form of micro- 
scope, for the purposes of clinical instruction and of class demon- 
stration. Over the body of the microscope, which is of small 
dimensions, a tube is fitted with a bell-shaped mouth at the end. 
This tube slides freely over the body, but is capable of being 
fixed at will, by means of a clamping-screw. The slide contain- 
ing the object is placed across the bell-mouth, and held there by 
a spring pressing against the back of it, and is thus maintained 
perpendicular to the axis of the instrument. When the focus is 
adjusted, the clamping-screw is fixed, and the fine adjustment 
necessary for the differences of vision in different individuals 
is effected by drawing out or pressing in the eye-piece. The 
object and object-glass are thus protected from mutual injury, an 
accident of by no means unfrequent occurrence in careless or 
unpractised hands. In this form the instrument is adapted to 
the clinical examination of secretions, &c., and must be directed 
by the hand towards day or artificial light. For demonstration 
to a class, this instrument is attached horizontally to a small 
wooden stand by means of a clamp, supported by two legs. To 
the stand a small oil lamp is likewise attached; and a stem pro- 
ceeding from the lower edge of the bell-mouth carries any desired 
form of condensing or illuminating apparatus. This stand is 
capable of being freely handed round a large class, without the 
focus becoming at all deranged, even when a very deep objective 
is employed. Professor Beale also exhibits, attached to micro- 
scopes of this form, some very beautiful preparations, illustrative 
of a fact discovered by himself, which has a very important phy- 
siological bearing—namely, that if small portions of tissue are, 
immediately after the extinction of life, immersed in an alkaline 
solution of carmine, those elements in which growth or develop- 
ment was actually in progress at a time immediately preceding 
the cessation of vitality, become permanently stained by the 
colouring matter; while from the “ formed material,” as he terms 
it, comprising those portions of tissue in which the development 
is complete, the colour may be subsequently washed out. This 
evidently affords a most important means of investigating the 
