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. 



