136 DESIGN IN NATURE 



the grey protoplasmic mass that the power of the ganglia chiefly resides. It is the grey matter of the ganglia which 

 converts sensory into motor impulses, and which is the active agent in thinking and in voluntary movement. 



Some of the gangha may very well be regarded as independent nerve centres, exercising what is virtually brain 

 power. The more highly differentiated gangha may not inaptly be designated brainlets or httle brains, that is, 

 microscopic collections of grey nerve substance with a measure of latent brain power. They can act directly after 

 the manner of brains, and as apart from irritabihty, artificial stimulation, and so-called reflex action. 



While the brainlet does not represent the brain, it is nevertheless a part of the same whole, and essentially the 

 same in kind. 



I append figures of gangha from the cerebro-spinal system of nerves, with the sensory and motor nerves which 

 enter and leave them. Numerous other examples of gangha are figured in other parts of the work. 



PLATE LVIII 

 Plate Iviii. shows the general resemblance of the several kinds of ganglia or nerve centres in the different 

 animals and parts thereof. The gangha are highly complex both as regards their structure and function. This is 

 especially the case in the spinal cord and brain. The brain is a continuation and expansion of the spinal cord, 

 and the nerve centres and elements found in the latter are repeated in the former. It is a question less of kind 

 than of degree, the brain being the more highly developed and differentiated of the two. 



Fig. 1. — Multipolar ganglion cell from the anterior horn of the spinal cord of the ox ; a, axis cylinder process ; b, c, d, e, branched 

 processes, x 300 (after Dieters). 



Fig. 2. — A. Three bipolar ganglion cells from the ganglion Gasserii of the pike. Tlie ganglia are seen at a, b, c (after Bidder). 



B. Three bipolar ganglion cells from the auditory nerve of the pike. At d, they are invested by the medullary sheath. At e, 

 they are partially exposed ; and at /, wholly exposed. Figure B, shows the ganglion cells to be mere dilatations of the axis cylinder 

 (after Max Schultze). 



Fig. 3. — Ganglion cells from the electric lobes of the brain of the torpedo. Medium-sized specimen, x 600. a, Axis cylinder 

 process ; b, b, 6, b, branched processes. Recent. Prepared by .short maceration in serum containing a little iodine (after Max Schultze). 



Fig. 4.- — A medium-sized ganglion cell from the anterior horn of the spinal cord of the calf, a, Axis cylinder; b, 6, b, b, b, 

 branched processes abruptly broken off (after Max Schultze). 



In discussing the fines of communication and of force in plants and the lower animals, I have alluded inci- 

 dentally to what may be regarded as rudimentary sensation, perception, and a low form of cognition. I shall have 

 occasion to return to this subject when I come to speak of the nervous system and of the reasoning powers of the 

 higher animals, where consciousness, memory, judgment, and many other attributes of mind have to be predicated. 



ATOMS, MOLECULES, AND CELLS AS FACTORS IN ORGANIC STRUCTURE 



AND FUNCTION 



The growth and movements of plants and animals are very largely, indeed principally, due to changes occurring 

 in the atoms, molecules, and cells, which enter into the composition of their bodies. 



An atom is defined as an ultimate, invisible particle of matter. It is the most minute portion of a chemical 

 element which can exist in a compound. Atoms are never free. They combine to form molecules, and, according 

 to Dr. Thudichum, as many as 1895 atoms enter into the formation of a molecule of hsematocrystalfin. 



The molecules, in turn, combine to form cells and tissues. The atom and molecule supply the basis of all 

 matter, organic and inorganic.^ 



> While the foregoing is the account given of the atom in woi-ks on chemistry, it is important to point out that of late years an electrical 

 theory of matter has been propounded, which, if it prove correct, will entirely alter our views as to the non-divisibility of the atom. 



In a lecture delivered at the Royal Institution of C4reat Britain (2nd March 1906), Professor J. J. Thomson of the Cavendish Labora- 

 tory, Cambridge, is reported to have stated that the old atom of the chemists since Dalton's days has gone, and in its place we now have cor- 

 puscles which make up the atom ; and instead of its being a single indivisible unit, it is regarded rather as a system of bodies, not unlike the 

 sun and the planets, and there is among the most recondite physicists a sort of "planetary theory of the atom." Following 'up Sir William 

 Crookes's experiments with his famous tube, Professor Thomson set to work to find the mass or weight of the electric particles that are thrown off 

 when a current is sent through a high vacuum. He found that some of these particles were not more than the one-thousandth part of the mass of a 

 hydrogen atom, and he gave them the name of corpuscles. The particles in question were all charged with negative electricity and either thev 

 were electricity itself or they were the carriers of electricity. On the former view they have been named electrons. One startlino- result of the 

 Professor's research was that the mass of the so-called corpuscle was always the same, no matter of what material' the electrode was made from 

 which the current was passed through the tube ; and this seems to mean that these corpuscles, or sub-atoms, or electrons are "the ultimate 

 particles, common to matter of all kinds," the protyle, of which Sh' W. Crookes prophesied many years ago. If matter is an electrical manifesta 

 tion, what then is electricity ? Dr. Larmor replies in an abstruse theory. It is a state of intrinsic strain in the universal medium or ether Our 

 electrical apparatus are machines for producing this strain. It was at first a grave objection to this doctrine that if atoms are made up of electrons 

 or corpuscles they must be liable to break up, and the breaking up of an atom was then unknown. Kadium disposed of that difficultv for radium 

 is visibly breaking up. Professor Thomson explained the processes by which he had measured the corpuscle proved it's plentn'ool a/o',.„„+„., j 

 measured its velocity—from 2000 to 60,000 miles per second. '^ >-« I'-s eiecwicai cnaiaetei, and 



