354 



NATURE 



[November io, 1921 



Prof. Hopkins has lately isolated an autoxidisable 

 substance from a number of tissues. It is a dipeptide 

 containing glutamic acid and cystein. This peptide 

 exists in two forms, one oxidised, in which two mole- 

 cules of dipeptide unite through their sulphur atoms 

 u> form a double molecule. The double molecule is a 

 liydrogen acceptor whilst the single molecule sulphhy- 

 drate is a hydrogen donator. This reversible reaction 

 allows the dipeptide to act as an intermediate sub- 

 stance in tissue oxidation, so that the rate of the 

 double reaction may be twenty times as fast as the 

 rate of oxidation in the absence of the dipeptide. The 

 reduction of the disulphide to sulphhydrate requires 

 the presence of a specific tissue enzyme. 



The nature of the hydrogen donators in the tissue 

 is not determined, but lactic acid is one of them, with 

 the formation of pyruvic acid. 



In his concluding remarks Prof. Hopkins appealed 

 to younger chemists to take an interest in the 

 problems of metabolism as their solution requires 

 chemically trained minds. He pointed out that the 

 reactions which take place in living tissues are not 

 different from those which take place in the laboratory, 

 but that they take place under different conditions. 

 In living tissues catalysts play an important part, 

 and chemical science will not be complete until the 

 nature of catalvtic reactions are explained. 



A number of speakers took part in the debate, and 

 the participation of chemists in biological work was 

 urged by several speakers. 



Photosynthesis. 



Following the discussion on oxidative mechanisms, 

 a paper by Prof. E. C. C. Baly, Prof. I. M. Heilbron, 

 and Mr. W. F. Barker was read on the synthesis of 

 formaldehyde and carbohydrates from carbon dioxide 

 and water. This study was the outcome of an in- 

 vestigation into the combination of hydrogen and 

 chlorine under the influence of light. It \yas found 

 that the rate was not proportional to the intensity of 

 light. It was suggested that the infra-red oscillation 

 frequencies of hydrochloric acid contained some 

 frequencies characteristic of chlorine, thus the first- 

 formed hydrochloric acid could autocatalytically 

 activate more chlorine. 



Carbon dioxide absorbs short wave-lengths in the 

 ultra-violet, but it is not affected by visible light. By 

 passing a current of carbon dioxide through water ex- 

 posed to ultra-violet light it is possible to show the 

 formation of formaldehyde. The previous experi- 

 ments of Moore and Webster required the presence 

 of an inorganic catalyst, but their failure to show 

 formaldehyde in the absence of the catalyst was prob- 

 ably due to too rapid polymerisation of the formalde- 

 hyde. The stirring effect of carbon dioxide passing 

 through the fluid allows some of the formaldehyde to 

 escape polymerisation. 



The visible rays require a photocatalyst with an 

 infra-red vibration of the same frequency as the carbon 

 dioxide. Chlorophyll absorbs visible light, and as it 

 forms a compound with carbon dioxide it can pass on 

 the trapped energy to the carbon dioxide. Malachite- 

 green, methyl-orange, and other dyes which can com- 

 bine with carbon dioxide likewise catalyse carbon 

 dioxide, so that formaldehyde is formed by the action 

 of visible light. 



Similarly polymerisation of formaldehyde requires 

 a coloured substance which can unite with formal- 

 dehyde. 



The photo-equilibrium of 



is difficult to demonstrate because formalde-hyde is 

 oxidised to formic acid by hydrogen peroxide, but the 

 reactions of carbon dioxide — ► formaldehyde and 

 formaldehyde — - sugar are both catalysed' by pigments 

 in visible light. 



Formaldehyde is not detectable in plants because of 

 its rapid removal. The chlorophyll absorbs the rays 

 which decompose sug'ar, hence the above equilibrium 

 becomes 



hexose carbon dioxide 



\ / 



formaldehyde 



Melanesian Land-tenure. 



A T a meeting of the Royal Anthropological Institute 

 ■^*- held on October ii i)r. W. H. R. Rivers, presi- 

 dent, gave an account of the Melanesian system of 

 land-tenure. He described the nature of the owner- 

 ship of land in two patrilineal societies in Melanesia, 

 Ambrim in the New Hebrides, and Eddystone Island 

 in the Solomons, and showed that its essentially 

 communistic character agreed with the account given 

 by Codrington of the land-tenure of the matrilineal 

 parts of the archipelago. This close agreement, con- 

 trasting with the great diversity of other aspects of 

 Melanesian culture, was held to indicate that the 

 communal ownership of land was an early, though 

 not necessarily the earliest, feature of Melanesian 

 society which has been little affected by the many 

 influences to which the general diversity is due. 



The fact that chiefs in Melanesia have no special 

 privilege in relation to land, and may even be wholly 

 landless, supports this conclusion, for there is reason 

 to believe that the present chiefs of Melanesia are the 

 descendants of relatively late immigrants. 



The ownership of trees, apart from that of the land 

 on which they grow, and the different laws of inherit- 

 ance to which the two kinds of property are subject 

 were described, as well as the customs by which the 

 produce of certain trees is assigned to individual use 

 by means of religious ceremonial. These customs 

 were explained as concessions made to immigrants 

 by the indigenous owners of the soil, who, while deny- 

 ing to strangers all rights in the land itself, allowed 

 them to own trees and transmit them to their children. 

 It was suggested that in some cases, and especially 

 when individual ownership or usufruct has a religious 

 sanction, the trees concerned mav have been intro- 

 duced by immigrants. The whole situation in relation 

 to the ownership of trees and land was regarded as a 

 characteristic instance of a compromise formation by 

 which was solved a conflict between the communistic 

 sentiments of an indigenous people and the indi- 

 vidualism of immigrants. 



hexose 



carbon dioxide 



\ / 



formaldehyde 

 NO. 2715, VOL. 108] 



University and Educational Intelligence. 



Bristol. — The Imperial Tobacco Co. (Great Britain 

 and Ireland), Ltd., Bristol, has contributed the sum of 

 10,000/., and Mr. C. H. Baker the sum of 5000/., to 

 the fund now being raised for the development of the 

 University. 



Cambridge. — The University has presented an 

 address to Dr. G. D. Liveing, St. John's College, 

 formerly professor of chemistry, to commemorate the 

 fact that he has kept by residence every term in the 

 University for the last seventy-five years. Dr. 

 Liveing graduated as eleventh wrangler in i8!:;o, and 

 was top of the First Class in the Natural Sciences 

 Tripos in 1851, the first year in which the examina- 

 tion was held. He became fellow of St. John's 

 College in 1853, and professor of chemistry in 1861. 



