December 27, 1917] 



NATURE 



ZZ7 



that period, been developed to the dignity of voluminous 

 quantitative sciences, whilst this section of the subject, 

 which is of great antiquity, can be dealt with on a page 

 or two of a text-book, and consists of incoherent quali- 

 tative facts. 



A recent paper by Dr. P. E. Shaw (Proc. Roy. Soc, 

 November, 1917) discloses interesting results, and in- 

 dicates that this neglected field of research is being 

 developed. Throughout the experiments described the 

 conditions of the surfaces used were varied systematic- 

 ally — by rise of temperature before and during friction ; 

 by treatment when fiexed; and by previously grinding 

 or polishing, and so on. it is well known that there are 

 condensed films on the surfaces of many solid mate- 

 rials. Little is understood as to the nature or depth 

 of these adsorbed layers, but they have proved a verit- 

 able stumbling-block to the investigator of certain 

 phenomena — ^t'.^'. surface-tension and photo-elecjtricity. 

 But these films have little influence on tribo-electric 

 effects, for here there is always a rough impact of 

 solid on solid, the films are penetrated, and the true 

 solid surfaces bear on one another. 



The tribo-electric series consists of thirty-six places 

 in order from the extreme + at top to the extreme — at 

 bottom. The outstanding feature of the present results 

 is the readiness with which a solid changes its place 

 in the series when its surface condition is changed by 

 heat, abrasion, flexure, and the like. Thus ordinary 

 soda-glass drops from place 5 to place 21 when made 

 matt, and to place 26 when its temperature has been 

 raised to 245° C. Mica, which normally occupies 

 place 6, drops to place 18 when matt, and to place 26 

 when heated to 270°. On the other hand, ebonite rises 

 from place 28 to place 27 when matt, and to place 21 

 when heated to 100°. The remarkable character of 

 these changes is that they are not erratic, but follow a 

 simple law, as follows : All materials in the series above 

 place 14 fall when rendered matt or after heating ; but 

 all materials in the series below 14 have the contrary 

 tendency, and rise when heated or made matt. Thus 

 the tendency is for the two ends of the series to come 

 together as a result of these changes of condition. The 

 temperature at which the change by heat occurs is 

 quite definite for each material, and has been found 

 for some sixteen metals and non-metals. It ranges 

 from 70° C. to 300° C. 



Dr. Shaw considers that this diametrically opposite 

 behaviour in the + and - groups of the series indi- 

 cates the existence of two kinds of atom or atomic 

 group, one kind for each group, the difference between 

 the two kinds being fundamental. But whatever form 

 the theory of these effects may take, these new facts 

 can scarcely fail to be of great importance. The re- 

 search provides an explanation of the well-known 

 readiness with which materials change their tribo-elec- 

 tric character. It should now be possible to avoid, in 

 great measure, the confusion and irregularitv which 

 have hitherto characterised the subject. 



THE RELATION BETWEEN CHEMICAL 

 CONSTITUTION AND PHYSIOLOGICAL 

 ACTION.'^ 



T 



HE rcl.ition between chemical constitution and 

 physiological action occupies a definite and im- 

 portant place in the study of drugs. Chemical investi- 

 gation of a drug begins with the attempt to isolate the 

 principle to which its activity is due. Then follow 

 the determination of its cx)nstitution and the syn- 



1 Summary of a lecturr delivered before the Chemical Society o" 

 December 6 by Dr. F. L. Pyman. 



thesis of a number of substances related to the 

 parent compound, and comparison of their physiological 

 action. . 



The wideness of the term "physiological action," 

 covering as it does any action on the living organism, 

 renders its discussion difficult. It is impossible, for 

 instance, to compare the bactericidal action of phenol 

 with the hypnotic effect of diethylbarbituric acid, or 

 with the anaesthetic action of cocaine, for the same 

 superficial signs of physiological action may be due to 

 widely different causes. Examples of physiological 

 action are not wanting. Compounds of similar con- 

 stitution generally possess a characteristic group- 

 smell, whilst each member may have a specific odour. 

 Sense of taste also provides an occasional means of dis- 

 crimination not onl> between side-chains of different 

 j length, but also in certain cases between stereo- 

 isomerides. 



Stereochemical influences often exercise profound 

 effects, particularly on nerve-endings. Thus Z-hyos- 

 cyamine has about a hundred times the mydriatic action 

 of d-h\x>scyamine, and Z-adrenine many times the pressor 

 effect of the dextro-compound. Asymmetry of a nitrogen 

 atom may also condition a difference, as in the case 

 of the a- and ^-methochlorides of Z-canadine. The 

 cause of this variation still remains in doubt. 



The influence of physical properties, such as solu- 

 bility in different media, may be of importance, and 

 it has been shown that for a particular series of 

 aliphatic compounds their narcotic effect on tadpoles 

 was proportional to the partition-coefficients of their 

 solubilities in oil and water. 



As an indication of the effect of chemical properties, 

 it has been shown that whilst certain basic dyes stain 

 the grey nerve substance, their sulphonic acids do not. 

 This difference suggested that bases, liberated in the 

 blood-stream by alkalis, are extracted by the nerve sub- 

 stance, whilst their sulphonic acids remain in solution 

 as alkali salts. 



In the case of alkaloids it is a general rule that the 

 introduction of a free carboxyl group profoundly modi- 

 fies the physiological action. Benzoyl ecgonine, of 

 which cocaine is the methyl ester, has no local an- 

 assthetic action ; whilst quitenine, obtained from 

 quinine by oxidation of the vinyl group, is non-toxic. 

 Formation of quaternary salts has also a considerable 

 effect. For instance, papaverine has a strychnine- 

 like action which is missing in its methochloride, 

 and reappears in its reduction product laudano- 

 sine. 



In the many cases in which members of a group of 

 compounds of similar constitution resemble one 

 another in physiological action it is of interest to ob- 

 serve the effect of slight chemical alterations. The 

 following four pieces of work were then outlined : — 

 (i) Tropeincs (aryl derivatives of the amino-alcohol 

 tropine); (2) aiin>ioalhvl esters (formed by the esterifi- 

 cation of an acid with an alcohol containing an 

 amiHO-group) ; (;^,) adrenine and the amines (adrenine is 

 the active principle of the suprarenal gland); (4) pro- 

 tozoacidal druf^s. The results of experiments that have 

 been made on the relative toxicity to infusoria of a 

 number of cinchona derivatives, with a view^ to their 

 employment in the treatment in malaria, indicate that 

 ethylhvdrocupreine "vas the most active, but they do 

 not admit of anv certain conclusions as to the relation 

 between their chemical constitution and protozoacidal 

 action. 



Experiments hnve also been made on the relative 

 toxicity of \\m- ipcracuanhn alkaloids to amoebae, and 

 thry indicah^ ihat the full amoebacidal action char- 

 acteristic of <Mnetine is exhibited only when the nucleus 

 is intact. 



NO. 2513, VOL. 100] 



