138 DESIGN IN NATURE 



Professor J. Hughes Bennett thus describes a molecule : " By a histological molecule is to be understood a 

 minute body, seen under high magnifying power in all organic fluids and textures, varying in size from the four- 

 thousandth of an inch down to a scarcely visible point, which may be calculated at less than the twenty-thousandth 

 of an inch in diameter. The smallest molecule has never been reached, even with the highest magnifying power. 

 In the same manner that the astronomer with his telescope resolves nebulae into clusters of stars, and sees other 

 nebulffi beyond them, so the histologist with his microscope magnifies molecules into granules, and sees further 

 molecules come into view." 1 The world is infinite in detail as it is vast in its general plan. 



According to Bennett molecules are formed in two different ways. 



1st. By precipitation in fluids or semi-fluid substances. 



2nd. By the disintegration of previously formed tissues. 



The former he calls Mstogenetic, or molecules of formation ; the latter Ustolytic, or molecules of dismte- 



gration. • „ • 



The division of molecules into " molecules of formation " and " molecules of dismtegration is countenanced 



by the fact that in the embryo the germinal matter breaks up and re-combines. 



In the adult, moreover, "new matter is being constantly added to the body, and waste or effete products extruded 



from it. 



In the higher animals (man, for example) food before it can be assimilated must be reduced to the molecular 

 condition, when it is known as chyle. Until it becomes chyle it cannot enter the blood and take part in nourishing 

 the tissues. 



Molecules lend themselves to endless combinations and transformations, chemical, physical, and otherwise. 



The facts which favour the " molecular theory of organisation " are largely embryological in character. 



The most essential part of the egg is the vitellus or yolk. From this the body of the embryo is formed, and 

 the organs of the new individual developed. The yolk of the egg, however, is granular, that is, it is composed of 

 molecules. These molecules, there is reason to beheve, vary infinitely as regards substance, form, and function. 



Molecules form cells and many other structures, such as the vitelhne membrane, the sarcolemma, neurilemma, 

 the anterior and posterior layers of the cornea, the capsule of the crystalhne lens, &c. Even the brain is 

 largely molecular. 



Molecules are necessary to hfe and reproduction. The Protozoa consist exclusively of molecules. They never- 

 theless live, grow, and reproduce themselves perfectly. 



It may be stated, broadly, that the primary act of generation both in vegetables and animals is due to the 

 presence of molecules, variously constituted and variously combined. The following is the account given by Professor 

 J. Hughes Bennett of the part played by molecules in reproduction : — 



" In the higher animals there are male elements, consisting of molecules, generally with, but sometimes 

 destitute of, vibratile filaments ; and female elements, composed of the yolk within the ovum, containing a germinal 

 vesicle or included cell. Both spermatozoid and germinal vesicle are dissolved in the molecules of the yolk, which 

 then, either wholly or in part, by successive divisions and transformations, constitute a germinal mass out of which 

 the embryo is formed. The male and female elements are, moreover, themselves molecular to begin with. Here, 

 as in plants, it is necessary to remember that the spermatozoids, the yolk, and the germinal mass, are aU composed 

 of molecules, and that these, combining together, form the nuclei, cells, fibres, and membranes which build up the 

 tissues and organs of the individual. It is not from either the male or female element that the embryo is formed. 

 The essential action is not so much connected, as has hitherto been supposed, with the cell wall or nucleus, as with 

 the molecular elements of the ovum. Many histologists, it is true, employ different expressions in referring to the 

 primitive molecular material from which organisation proceeds : thus it is the ' organised concrete ' of Haller ; the 

 ' sohdescible nutritive fluid ' of Wolff ; the ' primordial mucous layer ' of Burdach ; the ' sarcode ' of Dujardin ; the 

 ' blastema ' of Schleiden and Schwann ; the ' prohgerous pelhcle ' of Pouchet ; the ' germinal matter ' of Beale ; 

 the ' protoplasm ' of Kemak, Von Mohl, and Klihne ; the ' embryo plastic matter ' of Eobin ; the ' primordial 

 protogenes ' of Haeckel, &c., all which terms express essentially the same thing." ^ 



Professor J. Hughes Bennett, Professor T. Huxley, Dr. Lionel S. Beale, and others, regard the molecular basis 

 or blastema of the egg as homogeneous and identical in all its parts and particles, but to this view I cannot possibly 

 assent, for how, in reason, can tissues, organs, and organisms, infinitely diverse in ultimate structure and function, 

 be produced from material absolutely identical, seeing the conditions under which development proceeds are, 

 practically, the same ? It is not in the nature of things. 



1 "Physiology, General, Special, and Practical," by John Hughes Bennett, M.D., F.R.S.E., Professor of Physiology in the University of 

 Edinburgh, &c. 1872, pp. 36, 37. ■' 



' Professor J. Hughes Bennett, op. eit., p. 104, 



