September 14, 191 1] 



NATURE 



361 



blood corpuscle is perhaps the simplest task in physiology. 

 By the aid of the centrifuge these bodies can be obtained 

 free from the embarrassing presence of other cells, may 

 even be washed and immersed in definite solutions of 

 known value. In addition, these compressed discs — the 

 study of the forces normally compressing them open to 

 research by variations in the quality of the surrounding 

 solutions — contain no nuclear reactions, and but the one 

 material of primary dynamic importance. 



Everyone knows, however, that even in this case the 

 dynamic conditions are being investigated largely in an 

 indirect fashion. The materia! of primary importance, 

 hemoglobin, is stable except with regard to the one well- 

 defined reaction with oxygen to which it owes its utility. 

 This material may readily be obtained pure and its 

 properties examined in homogeneous solutions, and these 

 properties may again be studied after adding to this 

 solution such secondary substances, lipoids and inorganic 

 salts, as are also present in the red blood corpuscle. In 

 the hands of members of this section such studies are not 

 only increasing our knowledge of the properties of haemo- 

 globin, but are also rapidly leading to a knowledge of those 

 very dynamic conditions with which it is surrounded when 

 present within its microscopical site in the red blood 

 corpuscle. In this very simple instance, the parts of the 

 mechanism being known, it is possible to arrange them in 

 such a fashion as to limit our conceptions of the way in 

 which they are actually arranged within the body. 



In cases of greater complexity, where no doubt in course 

 of time the same method of indirect attack will be adopted, 

 in preparation for this event, the necessities of the moment 

 largely confine our attention to a discovery of the various 

 parts present in these mechanisms. In fact, the first 

 requirement is a knowledge of the micro-chemistry of these 

 more complex structures, that is to say, a precise know- 

 ledge of the chemical materials distributed in minute spaces 

 of microscopical dimensions. It is well known that my 

 predecessor in this honourable post, Prof. Macallum. of 

 Toronto, has contributed largely to our knowledge of these 

 matters, and that he further assisted us to a right concep- 

 tion of the forces in action between these minute masses of 

 material by his excellent Presidential Address to this 

 Section. 



Thinking of the body as no more than a collection of 

 chemical reactions, this elaborate separation of parts in a 

 multiplicity of extremely small spaces protects the indi- 

 viduality of a certain large number of reactions, whilst at 

 the same time securing a rich maintenance of contact with 

 supplies of raw material and a ready means for separating 

 the end-products of reactions from the materials in reaction 

 at each point. Every nucleus, surrounded by its constella- 

 tion of secondary chemical reactions, is thus given certain 

 limits of size, surface, territory, and environment. These 

 are physical necessities of arrangement possible within the 

 conditions of solution met with in the body, and no doubt 

 largely due to physical states developed by each reaction — 

 that is to say, that the products of each reaction exert a 

 physical influence and produce characteristic physical 

 arrangements. It is not without interest to realise that 

 cell-growth, and the increase in nuclear surface with 

 which it is attended in cell-division, is apparently initiated 

 at every centre by what is doubtless a physical process, 

 and what, as Loeb has shown us, may be accelerated bv 

 definite physical change. Such effects of growth are best 

 studied in those early days of enormous expansion when 

 the ovum increases to one thousand million times its 

 original weight, and it is at this time that these separative 

 physical consequences of chemical reactions are most 

 apparent. 



During this primary expansion not only have the 

 reactions of nuclear matter been extended to occupy some 

 hundred million times moie mass, but it is also true that 

 thev have been modified in a very large number of wavs, 

 and doubtless this as the consequence of special conditions, 

 extrinsic conditions, existing at the time of formation of 

 each separate part. These modifications are largely shown 

 by differences in appearance and structure, and are each 

 attended by some difference in the function of typical 

 groups of cells. A singular persistence in the similarity of 

 structure and function exhibited by successive generations 

 of similarly placed cells is no doubt sometimes due to the 

 NO. 2l85, VOL. 87] 



maintenance of those special extrinsic conditions which 

 occasioned their initial modification. In these cases rever- 

 sion to an original type may occur on immersion in 

 formerly pre-existent conditions, and indeed a whole series 

 of different structures make their appearance as the con- 

 ditions are further variously modified, as is sometimes seen 

 in the regeneration of parts. 



There is, however, seen in some cases a greater degree 

 of persistence, studied, for example, in malignant growths, 

 which is largely retained even when the extrinsic con- 

 ditions are greatly modified ; and in such cases there has 

 doubtless occurred some elimination and refinement — that 

 is to say, rather an abstraction than an addition of 

 character — as the consequence of the initial modification. 



In certain places in the adult, physical conditions due 

 to the modification and acceleration of chemical reactions 

 are still frequently provocative of nuclear growth and sub- 

 division : thus in the tonsils, follicles, patches, and 

 lymphatic structures generally, that are embedded in the 

 surface of the alimentary canal. These structures, charac- 

 terised by their great wealth of nuclear material, experi- 

 ence great nuclear change, to which they are largely 

 stimulated by chemical substances derived from foreign 

 organisms. Specifically affected by each chemical sub- 

 stance, they are probably the site of manufacture of specific 

 neutralising substances that are driven from these "sites of 

 activity into the portal system almost as soon as the 

 substances exciting their appearance are driven in from the 

 absorbent surface of the alimentary canal. 



In other places in the adult, however, such conditions 

 never recur after a certain date in development. In these 

 places the nuclear material has been so refined as to be 

 irresponsive to conditions that accelerate and modify the 

 reactions of nuclear material in other parts. Permanent 

 sites of monotonous nuclear activity are formed and main- 

 tained in such places until the moment when some 

 unusually extreme condition still further limits their 

 activity and terminates their existence. It is significant, 

 too, that this may happen when the condition is not 

 sufficiently extreme similarly to cut short the reactions of 

 other parts. 



Now the latter case is typically illustrated by reference 

 to the nervous system, which is thus seen as the site of a 

 severely limited quality of chemical activity. That it is 

 also restricted in amount may be further emphasised by 

 reference to the relatively minute quantity of nuclear 

 material which is present in this system. Thus it is 

 probable that if a direct comparison between the cells of 

 the nervous system and the lymphoid cells to which I have 

 alluded were possible, the essential difference found would 

 be a difference between the stability of certain chemical 

 material in the one case, and a frequently modified wealth 

 of chemical reaction in the other ; so that of the two, the 

 nervous system would be the more comparable with the 

 red blood corpuscle. 



Thus, if when reviewing the wide array of function in 

 which the nervous system participates, we are led to 

 foresee for each of its cells a great variety of chemical 

 change, or, if when surveying the great differences in 

 function of the organs of the body we are led to expect 

 typical chemical differences between those several parts of 

 the central nervous system with which they are individually 

 associated, we are arrested bv this clear evidence of a 

 universally distributed monotony of simple chemical state. 



It is true that certain drugs affect some groups of cells 

 within this system more readily than others. None of 

 these instances are, however, of such a kind as to demand 

 the inference that there was any essential difference 

 between different groups of cells. In most cases, indeed, 

 it is probable that differences in relative quantity, and in 

 such simple factors as relative state of solution, are 

 responsible for these effects. Thus there is nothing to 

 refute the statement that all the cells of the nervous system 

 contain chemical materials of an exactly similar kind. Just 

 as every liver-cell is like every other liver-cell in its 

 general chemical character, so in the nervous system are 

 all the cells chemically alike. 



Glancing from the liver-cell to the nerve-cell, however, 

 there is at once seen a marked difference of a kind we 

 have not yet considered. The chemical experiences of the 

 liver-cell are multifold, but in the main alike for each cell, 



