6

4. A description of the parasites.

      When the bodies are present at all, they are usually to be found in large
numbers. They are seen with difficulty in fresh preparations, but can be detected
and distinguished from blood platelets. They are rather more refractile than
platelets and often have a faint greenish tinge. One or two more refractile
masses can be made out in the body of the parasite and in many cases an appear-
ance like a grain of pigment is seen. On careful focussing this is seen to be a
minute refractile spot like " Manson's spot " in lymphocytes. The bodies are
quite motionless.

      In films stained by Romanowsky's method the bodies are seen with great
clearness. They exhibit a remarkable uniformity in size and appearance. The
majority are about 2.5 micromillimetres in diameter, but forms may be found
which are a little larger, 3 to 3.5 micromillimetres, or a little smaller, 2 micro-
millimetres. Very occasionally still smaller bodies, 1.5 micromillimetres in diameter,
may be encountered. Most of the bodies are approximately circular in outline,
but very many, and especially the larger forms, are irregularly oval and very much
resemble a cockle-shell in shape (Figures 7 and 8). This, indeed, appears to be
the most typical shape and even in the apparently round forms an approach to
this shape can be made out. Occasionally specimens are found more elongated
and distinctly pear-shaped.

      The bodies are very clearly outlined, and appear to possess a distinct and
comparatively resistant cuticle. They retain their proper shape and are very
rarely seen distorted. I have seen a body which had been crushed and from
which the two chromatin masses had been squeezed out. The larger mass still
lay partially within the body which had an appearance exactly resembling that of
a ruptured cuticle.

       The bodies are very resistant to hypotonic solutions and may be recovered
by centrifugalisation from blood that has been laked by such a solution.

       Except in very rare small forms which show only a single chromatin mass,
the bodies invariably possess two chromatin masses—a large one staining lightly
and a small one staining intensely with the red colouring matter of Romanowsky's
stain.

       The two chromatin masses are usually situated opposite to each other in the
shorter axis of the parasite.

      The small chromatin mass is usually rod-shaped, but may appear as a
dot only. It is usually contained in what appears to be protoplasm displaced to
the periphery of the body by the vacuole or vacuoles. It may appear close to
the periphery or centrally situated. In the latter case it is probably in reality