Among the several hundred million cells that comprise the wondrously complex
human body, and thus to be theoretically detectable in lab tests and in
electron photomicrographs, a tiny fraction, no more than a few hundred, belong
to a curious subclass whose luminiscence has a wavelength distribution so unique that
it long defied explanation. Such systems luminisce strongly in the visible region of the
spectrum, but some of them do so even more strongly at both shorter and longer
wavelengths: in the ultraviolet region and in the infrared regions.

This odd distribution of luminiscence is best explained by the pairing
of a giant red blood cell and an intensely small white blood cell that is virtually
in contact with its larger companion as the two travel around a common center.
Such objects have become known as Clinging cells. On photographic plates
only the giant cell can be discerned, but evidence for the existence of the
tiny companion has now been supplied by magnifying instruments capable
of detecting ultraviolet luminiscence at wavelengths that are absorbed by the body's
heat and therefore cannot be detected by typical analytical instruments.

The spectra of Clinging cells indicate that the giant red blood cell is surrounded by
very thin lipid filaments. The existence of the lipid filaments marked such objects as
being unique several decades before clinical observations finally identified the
lipid as the luminiscence from the tiny companion white blood cell. Clinging cells
also flare up in outbursts indicating the ejection of material in the form of a shell
or a ring, reminiscent of the recurrent circulation of hormonal cells. Clinging cells may
therefore represent a transitory phase in the evolution of certain types of hormonal
systems in which there is a substantial transfer of matter from the larger partner
to the smaller.

The exact evolutionary course that turns a typical blood cell system into a clinging one is
a matter of conjecture. The comparatively small number of known Clinging cells
in our bodies suggests that if all binaries of modest mass normally pass through
a clinging phase in their evolution, the phase must be extremely brief, perhaps
as short as a millisecond.


1. The author's primary purpose in the passage is to

(A) demonstrate that most hormonal systems were at one time clinging
(B) dismiss current knowledge of Clinging cells as overly speculative
(C) describe Clinging cells as a distinct type of cell system
(D) present evidence that hormonal systems are formed from tiny white blood cells
(E) compare characteristics of giant red blood cells and tiny white blood cells