26 



NATURE 



[November 3, 1910 



ance of the matter, and steps are being taken to distribute 

 these papers among agricultural experimenters. 



A paper by Mr. Collins on the errors of milk analysis 

 concluded the session. 



The position of agriculture at the British Association is 

 not yet settled. Whatever the council decide to do, it is 

 hoped they will continue to give a separate organisation to 

 agriculture, and thus afford to workers in agricultural 

 science an opportunity — the only opportunity for some of 

 them — of meeting their fellow workers in pure science and 

 discussing their problems. It is necessary to get help from 

 several sides and not simply from one, as from the chemical 

 or the botanical, which seems to be the theory of a sub- 

 section. However, whether lawfully or not (it appears to 

 have been unlawfully) the organising committee has 

 hitherto enjoyed the fullest liberty, and has succeeded in 

 arranging a series of meetings that have proved extremely 

 helpful to agricultural investigators, and promise to play 

 no small part in the encouragement of agricultural research. 



TUYSIOLOGY AT THE BRITISH 

 ASSOCIATION. 



T N addition to the presidential address, which has 

 ■*■ appeared already in Nature, there were a number of 

 interesting papers communicated to the section. Physi- 

 ology was unique in that it was the only section that 

 met at the University ; and thus, although somewhat 

 isolated from the other sections, enjoyed the advantage 

 of the laboratories for demonstrations. 



There were two joint meetings, one with Chemistry 

 (Section B) and Botany (Section K) on the biochemistry of 

 respiration, and the other with Education (Section L) on 

 speech ; the latter will be reviewed in the proceedings of 

 the section of Educational Science. In addition. Dr. 

 Leonard Hill, F.R.S., gave an interesting address on the 

 prevention of caisson disease. The individual papers will 

 be reviewed, as much as possible, so as to form groups 

 in a logical sequence. 



The discussion on respiration, held in the meeting-room 

 of Section K, was opened by Dr. F. F. Blackman, F.R.S., 

 who dealt with the subject under three headings. 



(i) The series of chemical reaction which take place 

 during oxidation. He took glucose as a typical example, 

 of which the final products are carbon dioxide and water, 

 but the intermediate steps are difficult to follow. 

 Buchner's zymase produces alcohol and carbon dioxide 

 from glucose, but it has been shown that alcohol cannot 

 be oxidised by plants, and hence it must be surmised that 

 some other substance, before the breakdown has reached 

 the alcohol stage, is what is actually oxidised. There are 

 probably many of these fugitive compounds, amongst 

 which- may occur lactic acid and di-hydroxy acetone. An 

 alkaline sugar solution, as the result of exposure to sun- 

 light, gives rise to substances which are easily oxidised. 

 He then dealt briefly with oxidases, peroxide formation, 

 and Palladin's hypothesis of respiratory chromogens, 

 which are oxidised by oxidases to peroxides, and then 

 pass on the oxygen to oxidisable material. 



(2) The physical chemistry of the processes involved in 

 oxidation. Influence of temperature on velocity of re- 

 action (usually shows a coefficient of about 2-5 within the 

 limits of temperature at which living processes can occur) ; 

 the uniformity of the respiratory quotient (O^/CO,) at 

 different temperatures and the effect of the concentration 

 of the reacting substances were discussed. He illustrated 

 these points by referring to his experiments with green 

 leaves and potatoes (starchy and rich in sugar). The 

 output of carbon dioxide by green leaves is reduced to 

 zero by exposure to sunlight. The potatoes rich in sugar 

 show a greater rate of oxidation than the starchy ones. 

 The conclusion is arrived at that there is a minimal tissue 

 respiration and an excess of respiration depending on the 

 supply of respirable material. 



The influence of accelerators, paralysators, and other 

 substances was mentioned. 



(3) Special influences of colloidal nature of cell proto- 

 plasm. Oxidation and reduction take place side by side, 

 and death of the cell mixes up these two processes. 

 Alterations of permeability of protoplasmic septa may 

 account for changes in physiological oxidation processes. 



NO. 2140, VOL. 85] 



Dr. H. M. Vernon referred to Dakin's work on oxida- 

 tion of fatty acids and amino-acids by hydrogen peroxide 

 and traces of ferrous salts. If zymase is allowed to act 

 upon glucose for a short time, then the solution is boiled 

 and oxidase and hydrogen peroxide are added, there is 

 almost complete oxidation to carbon dioxide and water ; 

 this suggests that oxidases may act in living cells if 

 organic peroxides can replace hydrogen peroxide. His 

 own experiments on survival respiration (kidney) point to 

 the presence of oxidases, and that certain poisons act by 

 combining with aldehyde or similar groups. Some sub- 

 stances act especially on the " high-grade " process (forma- 

 tion of carbon dioxide) and not so much on the " low- 

 grade " process (oxygen absorption), and thus the respira- 

 tory quotient is lowered. In relation to minimal proto- 

 plasmic and excess respiration, he directed attention to 

 the fact that minced tissues show at first a greater out- 

 put of carbon dioxide than when intact, but that the 

 respiration soon falls to a much lower level. 



Dr. E. F. Armstrong pointed out that in many respects 

 oxidases differed from the other kinds of enzymes (they 

 are heat stable and not specific in action), that their 

 action can be imitated by colloidal suspensions of inorganic 

 matter, and that traces of inorganic material are usually 

 present in them. There are, however, specific oxidases. 

 He then demonstrated the blackening of laurel leaves by 

 the action of toluol (other chemically inert substances with 

 little affinity for water act similarly), which he ascribed 

 to a general breakdown of the protoplasm with liberation 

 of oxidases. 



Mr. D. Thoday spoke about the result of experiments 

 on anaesthetised leaves. Small doses of chloroform cause 

 a temporary increase of oxidation. A large dose causes 

 a diminution in the output of carbon dioxide ; with 

 Helianthus and cherry laurel there is a great increase in 

 oxygen intake, which quickly falls off, but with 

 TropaK)lum the oxygen intake falls at once. It was sug- 

 gested that tannins oxidise first, and as there are no 

 tannins in Tropaeolum there is no initial increase of oxida- 

 tion. Probably the result is brought about by an increase 

 of permeability. 



Prof. H. E. Armstrong, F.R.S., referred to Leathes' 

 work on the splitting of fats at intermediate points in 

 the carbon chain, and to the formation of peroxides by 

 manganese and iron with hydroxy-acids. Oxidation may 

 take place by decomposing water with liberation of 

 hydrogen ; in plants the hydrogen may be used to reduce 

 carbon dioxide to formaldehyde. The leaf surfaces show 

 a permeability similar to that found by Adrian Brown for 

 barley grains. 



Prof. Waller and Dr. Reynolds Green spoke, and Dr. 

 Blackman replied. 



Dr. Leonard Hill, F.R.S., reviewed the work done in 

 relation to the prevention of compressed air illness. 

 Whilst exposed to high pressure the body dissolves a 

 larger amount of gas than at ordinary atmospheric 

 pressure, and when the pressure is reduced bubbles of gas 

 may be set free in the blood vessels. The solubility of 

 the gas follows Henry's law; owing to the capacity of the 

 tissues to absorb oxygen it is only the nitrogen that is 

 set free in the vessels. The symptoms depend on the por- 

 tion of the circulation which is stopped by the nitrogen 

 embolus. Different portions of the body saturate at 

 different rates, but work, by increasing the circulation, 

 increases the rapidity with which the body takes up and 

 gives off nitrogen. By analysis of the gases in urine it 

 can be shown that it takes an appreciable time for the 

 body to get into equilibrium with the pressure of the 

 nitrogen in the atmosphere, or, in other words, the blood 

 does not get into equilibrium with the gas on passing 

 once through the lungs. 



The relative merits of uniform decompression and de- 

 compression by stages were discussed. Long shifts are 

 better than short, as there are fewer decompressions for 

 the same amount of work, and the danger is due to 

 decompression. When symptoms occur they can be 

 abolished, or the danger minimised by recompression to 

 the original pressure. 



He recommended that, during decompression, occasional 

 inhalations of oxygen should be taken (to lower the 

 partial pressure of the nitrogen in the lungs, and thus 



