Page:Principles of Microscope.djvu/23

Rh preparation is mounted in air, is illuminated by narrow-angled beams and is viewed with a narrow-angled objective (vide p. 22, Exp. 1; p. 41 (b); and p. 42, Exp. 2).

b. A film preparation of blood in which the elements are delineated by bright outlines upon a dark field. (Dark ground illumination.) The preparation is mounted in water, is illuminated by hollow wide-angled beams (furnished by a wide-angled condenser fitted with a central spot stop as shown in Figs. 75 and 90), and is viewed with a narrow-angled objective (vide p. 23, Exp. 2).

c. Film preparation of blood seen as a picture in relief. The preparation is mounted in air, is illuminated by such a system of obliquely incident beams as is shown in Fig. 76, and as is obtained by the arrangement shown in Plate XII, Fig. 1 (vide p. 23, Exp. 4).

d. Film preparation of blood in which the elements are visible only in so far as they are coloured (colour picture). The preparation is illuminated by a focussed fully-open wide-angled condenser in the field of which is the window bar shown in the upper part of the figure (vide p. 23, Exp. 3; p. 99, Exp. 1, and p. 174).

e. Film preparation of blood in which the elements are differentially stained by Leishman's stain (vide p. 24).

f. Film preparation of blood stained diffusely with eosin (see p. 36, Exp. 6).

g. The same preparation partially discolourized by the agency of a weak alkali (see p. 36, Exp. 5).

h. The same preparation after further staining with methylene blue (see p. 36, Exp. 7).

PLATE IV (facing page 28).

A. Diagrammatic representation of a glass cell filled with transparent highly refractive spherules lying in air. The opacity of the contents of the cell is seen to be due to the fact that the rays which here pass up through the floor of the cell are diverted from their course by refraction and reflection (vide pp. 27 and 28, Exps. 1-4).

B. Diagrammatic representation of the same cell and spherules lying in a highly refracting enveloping medium. The transparency of the contents of the cell is seen to be due to the fact that the rays here pass upwards through the cell without being turned aside from their course by reflection or refraction (vide pp. 27-28, Exps. 1-4).

PLATE V (facing page 42).

Fig. 1. Diagram showing manner in which illumination by differentially coloured light is achieved in the case of a spherule placed in position as in Plate I D, against a parti-coloured radiant field (vide p. 17 (d) ). [sic]

Fig. 2. Vide p. 42, Exp. 2 and comment.

Fig. 3. Vide p. 42, Exp. 2 and comment.

PLATE VI (facing page 78).

A and B. Diagrams showing influence of aperture upon the definition of the focal images in the case of interpenetrating point vistas derived from radiant points placed one behind the other (vide p. 78, subsects. 17 and 18).