November io, 192 i] 



NATURF 



353 



two series of circles overlie one another exactly and 

 become identical with those of the latter arrange- 

 ment and similar to those of adularia. At 1190'^ C. 

 melting begins, and the spots disappear. Moreover, 

 as the temperature approached 1000'' C the schilleriza- 

 lion disappeared. Hence the schillerization of moon- 

 stone is due to the fact that interference of ordinary 



Ljht.ravs is produced by the presence of the two 

 uilTerent space-lattices corresponding to the two 



irrangements. 

 Similar investigation of the moonstone found ten 



. ars ago in Korea led to analogous and confirmatory 

 ; isults. This moonstone proves to be more sodic and 

 calcic than the Cingalese variety, and the two sets of 

 spots which its radiograms exhibit, corresponding to 

 two distinct sets of space-lattice net-planes, are 

 given bv plates parallel to the side pinakoid faces, 



whereas in the case of the moonstone from Ceylon 

 they were afforded by plates parallel to the basal 

 plane. On heating the crj'stal the schillerization dis- 

 appears, and the two systems of spots become coin- 

 cident at a temperature of 790° C, very much below 

 the melting-point of the crystal, which lies between 

 1100° and 1200° C. 



These Japanese investigators would thus appear to 

 have proved that in the cases of moonstone of Ceylon 

 and Korea, the beautiful schillerization appearance is 

 not due to the presence of inclusions and lucunae, aS 

 formerly believed, but to the existence of two distinct, 

 yet closely similar, space-lattices, which are so 

 arranged with respect to each other as to cause the 

 rays of ordinary light to interfere. It is very gratifying 

 that the worlc commenced by Mr. Kozu in Cambridge 

 has led to such interesting and important results. 



Tissue Metabolism. 



oxid.ation and oxidative mechanisms in 

 Living Tissues. 



AT a joint meeting of the Sections of Chemistry 

 and Physiology during the recent meeting of the 

 British Association at Edinburgh a discussion on the 

 above subject was opened by Prof. F. G. Hopkins, 

 who commenced by pointing out that the essential task 

 of biochemistry is dynamic. The task of investigation 

 is difficult because the living structure is easily 

 destroyed. In spite of this obstacle considerable pro- 

 gress has been made by various methods. 



In the oxidation of fatty acids it is now recognised 

 that the oxidation takes place in the ^-position. 

 Knoop investigated this problem by loading the fatty 

 acid molecule with a non-oxidisable group, namely, a 

 phenyl group. The side chain of fatty acid is oxidised 

 so that all the substances administered reappeared as 

 two substances. All those with an odd number of 

 carbon atoms were oxidised to benzoic acid which was 

 found in the urine como.ned with glycine as hip- 

 puric acid, whilst all those with an even number of 

 carbon atoms were oxidised to phenylacetic acid, which 

 was found combined with glycine as phenylaceturic 

 acid. This result suggested that two carbon atoms 

 were removed at each stage, thus there was no in- 

 dication that by removal of one carbon atom the 

 -cries with odd or even carbon atoms could be changed 

 from one to the other. 



Embden perfused fatty acids through the surviving 

 liver, and found that all those with an even number 

 of carbon atoms passed through the four-carbon stage 

 whilst those with an odd number of carbon atoms did 

 not pass through that stage. This, again, indicated that 

 a single carbon atom was never removed, so that the 

 odd and even carbon chains were not interconvertible. 



The fate of the two carbon atoms that are split off 

 has not yet been determined. It is interesting to 

 remember that large quantities of material are dealt 

 with in this manner, and that more than three 

 thousand tons of fatty acid are o.xidised daily in the 

 human body in this countn*'. 



It is probable that carbohydrates are not oxidised 

 directly, but that hexoses are converted into lactic 

 acid. In the study of this problem isolated muscles 

 are useful because the functional condition of muscle 

 can be tested by its ability to contract. The change 

 from hexose to lactic acid is probably associated with 

 the presence of hexose phosphate, a fact which links up 

 the metabolism of higher organisms with the fer- 

 mentation of sugar by yeast, in which hexose phos- 

 phate is an important intermediate stage. 



Surviving muscle, in anaerobic condition, loses carbo- 

 XO. 2715, VOL. 108] 



hydrate with the formation of lactic acid ; when 

 oxygen is readmitted the lactic acid disappears. The 

 removal of lactic acid is not due entirely to oxidation, 

 but about one quarter of the acid is oxidised, and three 

 quarters are reconverted into glycogen. Associated 

 with these changes it can be shown that muscle con- 

 traction can be divided into at least two stages, one 

 in which no oxidation occurs, and a later stage in 

 which recovery is associated with the disappearance 

 of oxygen. 



The fate of proteins is that they are resolved into 

 their constituent amino-acids, and the oxidation of 

 these individual acids must be investigated. The re- 

 sult of disease, and of the administration of drugs, is 

 to cause the appearance of intermediate products from, 

 which one learns that the amine group is removed by 

 oxidation giving rise to keto-acids. The behaviour of 

 acids with special groups in them furnishes further 

 information. In dogs kynurenic acid is the end pro- 

 duct of oxidation of tryptophane. If indole lactic acid 

 is administered it is found to be toxic, and it does 

 not give rise to kynurenic acid. The corresponding 

 keto-acid is not toxic, and gives rise to kynurenic 

 acid, showing that in this case the amine group is 

 removed from tryptophane bv oxidation giving rise to 

 the keto-acid, and not by hydrolysis giving indole 

 lactic acid as the intermediate substance. 



It is the outstanding feature of oxidation in living 

 organisms that they can take in molecular oxygen and 

 combust material at a temperature of not more than 

 38° C which are not combusted by molecular oxygen 

 at moderate temperatures outside the body. All cells 

 contain autoxidi sable substances with the apparent 

 formation of peroxides. Oxidising enzymes are found 

 in manv cells, some of which, however, need the 

 presence of a peroxide whilst others apparently can 

 form their own peroxide. In plants the peroxide- 

 forming substances are probablv something of a 

 catechol nature. The oxidases are usually studied by 

 the use of colour-forming indicators, 



Hydrolytic oxidation and reduction may also occur. 

 For instance, milk does not act by itself on acetalde- 

 hvde or on methylene-blue, but in a mixture of these 

 two milk causes an oxidation of acetaldehyde and re- 

 duction of methylene-blue. This is analogous to the 

 Cannizzaro reaction, where two molecules of benzal- 

 dehvde react, one being reduced to benzyl alcohol and 

 the other oxidised to benzoic acid. For this type of 

 reaction it is necessarv' to have an activation of 

 hvdrogen with a hydrogen acceptor, so that the oxygen 

 of water is set free to produce oxidation of some other 

 substance. 



