154 KEPORTS OX TfJE STATE OF SCIENCE. 



manuring has the effect of increasing the yield of prussic acid, and, 

 similarly, Treub ' found that the application of potassium nitrate led to 

 an increased production of prussic acid in plants of Phnseo/na lunafus. 



The results obtained by the prosecution of investigation in these three 

 directions lend support to Treub's view that prussic acid pl.ays some 

 important pai't in plant metabolism, and is probably a step in the process 

 by which these plants convert the ' inorganic ' nitrogen of nitrates into 

 the ' organic ' nitiogen of proteids. 



It may be wortli while, therefore, to refer to the \arious theories of 

 proteid formation in plants, which liave been put forward in which 

 prussic acid is regarded as a basis of proteid synthesis, or in whicii its 

 svidespread occurrence in plants is accounted for. 



On the theoretical side Pfliiger '' regarded the cyanogen radicle as a 

 most important factor in the constitution of the proteid molecule, and 

 advanced the hypothesis that whereas in ordinary proteid the nitrogeji 

 probably occurs in the form of amino groups, in the molecule of living 

 protoplasm it was probably present in the form of cyanogen radicles. 

 Dr. P. W. Latham, in his Croonian Lecture on 'Some Points in thn 

 Pathology of Rheumatism, t>out, and Diabetes,' also assigns an important 

 role to the cyanogen radicle and to prussic acid in the con.stitution and 

 natural synthesis of animal proteids.-' 



From the chemical side, however, more importance attaches to the 

 views put forward by Victor Meyer and Schulze, Bach and Gautior. 

 Meyer and Schulze suggested ' that the nitrates in cell sap are Jirst 

 reduced to hydroxylamine, which combines with the various aldeliydie 

 and ketonic substances occurring in plants forming aldoximes and 

 ketoxime.s, and that the oximino group subsequently undergoes reduc- 

 tion to an amino group. Bach's explanation ' greatly extended that put 

 forward liy Meyer and Schulze, This investigator supposed thaf, from 

 the small amount of nitrate present in cell-sap, nitric acid was liberated 

 in minute amount by the considerable quantities of oxalic and carbonic 

 acids usually present, and that this free nitric acid was continuously 

 reduced by formaldehyde, producing hydroxylamine, which immediately 

 combined with formaldehyde, foiming formaldoxime. The latter might 

 then undergo transformation in two ways. It might be convei-ted into 

 the isomeric formaraide, which l)y simple dehydration would give prussic 

 acid and water, and in this way account for the frequent occurrence of 

 this acid in plants, or the formamide might be hydrolysed, yielding 

 ammonium formate, so supplying ammonia and formic acid. 



There may be a fundamental objection to this view. Meyer and 

 Schulze have themselves shown that hydroxylamine is poisonous towards 

 protoplasm, but this difficulty of the genei-ation in the plant of a sub- 

 stance which is toxic to protoplasm, also occurs in the formaldehyde 

 liypotliesis of the phytosyn thesis of carbohydrates, and may perhaps lie 

 fiyercome by assuming that the hydroxylamine as it is formed is imme- 

 diately converted into a stable and innocuous oxime. 



On the other hand, there is indirect physiological evidence in favour 

 of this view. Thus the supposition that the reduction of nitric acid is 

 accomplished by formaldehyde is in harmony with the observation that, 

 whilst nitrates occur abundantly in stem structures of green plants, they are 



» I.O(f. cit. t ArcJiirfiir Physiologie. 1875, 10, 2.')I. 



=• Brit. Med. Jmirml, 18S6, 1, G29. * lier., 188t. 41," J 554. 



6 Afonitem Scientifique, 1897, iv. 11, 1, 



