Picture - Cosmic Polymath

332 DESIGN IN NATURE
subject is still sub judice. Kiiline showed that vegetable protoplasm placed within the intestine of a cockchafer
contracts like a muscle under the influence of electricity.
The movements of the white blood-corpuscles in red-blooded animals are especially deserving of study. In
shght local inflammations, such as are produced in the mesentery of a mouse by applying a weak solution of
mustard, the corpuscles in question are seen by the aid of the microscope to adhere to the interior of the capillary
blood-vessels, and gradually to force themselves through the capillary walls, assuming, as they do so, a great variety
of shapes. What generally happens, and what I myself have frequently observed, is this : the corpuscle projects
from its substance a wedge-shaped portion, which is forced into the capillary wall ; the remainder of the corpuscle
streams through the aperture so produced by what appears to be a pushing movement ;
once outside the capillary
vessels the corpuscle assumes its spherical form. The white blood-corpuscles are endowed with independent
vital movements. They are also credited with the power of combating and destroying inimical living organisms
which invade the blood and engender disease, often of a fatal character.
That hving organisms do infest the blood is proved beyond doubt by their being found in certain cases in
large numbers in the blood-plasma and within the red and white blood-corpuscles. This happens in malaria and
other diseases, as proved by the aid of the microscope. As the red blood-corpuscle in man measures only from the
^ It to the -tJWt- of an inch in diameter, I leave it to be inferred how very minute the malarial microbes are. As
' jUUU aOOU •111
a matter of fact, some of them have a diameter of only the ^o^ of an inch or thereby.
The manner in which malaria, plague, sleeping sickness, and other diseases are produced is now well under-
stood. The malarial and other microbes are introduced into the human skin and fluids of the body by the bite
of certain mosquitoes, the tsetse and other flies, and float about in the blood-plasma, where certain of them enter
the red and white blood-corpuscles, which act as hosts to the invaders. As the red and white blood-globules and
the microbes are both in motion, their coming in contact is generally a mere matter of time (Figs. 61 and 62,
page 306 ; Plate Ixxxii., Fig. 1, page 313).
Professor Huxley has figured the amoeboid movements of the blood-corpuscles of the cray-fish (Plate Ixxix., Fig. 6,
page 308).
It may be useful if at this stage I give a short account of the amoeba, paramecium, gromia, and other
rudimentary animal forms which supply information of a very important character, not only as regards movement,
but also as regards organisation and reproduction.
RUDIMENTARY FORMS IN RELATION TO MOVEMENT, REPRODUCTION, AND LIFE
§ 6o. AmcEba Proteus.
The amoeba is deserving of very special attention for three things : (a) its simplicity of structure ; [h) its
universaUty of function ; and (c) its extraordinary power of movement.
It is a rudimentary microscopic organism, varying from the ^-^ to the y^-^ of an inch in diameter, and is found
in the mud of streams and ponds. It has no definite shape, and resembles a drop of semi-hquid jelly.
It is a type of the sub-kingdom Protozoa, and consists of a simple cell ; it is an example of the phylum Gymnomyxa
(naked jelly), its protoplasm being freely exposed to the surrounding water and its whole body performing the
functions of ingestion, egestion, assimilation, respiration, reproduction, movement of various kinds, a low form of
sensation, &c. It is representative of the class Rhizopoda, as it throws out blunt pseudopodia or false feet from its
substance.
The amoeba, designated Amoeba proteus from its ever-varying shape, consists of a thin superficial layer of dense
clear protoplasm {ectoflasm), and a thinner interior protoplasm (endoplasm). In the latter are found food-vacuoles
with or without food ; a large contractile vacuole, filled with clear fluid, and a nucleus composed of mwleoflasm.
The food-vacuoles occupy various positions ; any part of the amoeba becoming a temporary stomach. The con-
tractile vacuole is endowed with the extraordinary power of closing and opening by centripetal and centrifugal
rhythmic movements, similar to those occurring in highly-differentiated hearts ; the vacuole opening slowly and
closing or contracting somewhat suddenly. The contracting vacuole communicates by a minute temporary canal
with the exterior, by which it ejects its fluid. It is beheved to be an excretory organ for the removal of
nitrogenous products.
The other matters found in the endoplasm consist of minute granules, small regular crystals, and sand and
other grains. The amoeba, it will be seen, is very far from being homogeneous in composition, although usually
regarded as such.
The general appearance of the amoeba is given at Fig. 68.