B.—CHEMISTRY. 41 
sue¢h voluminous complexity as to be unintelligible without the guidance 
of an expert, and in this capacity W. Jones has rendered valuable 
service by his recent lucid arrangement of the subject (1921). From 
this if is comparatively easy to follow the conversion of nucleic acid 
into uric acid through the agency of enzymes, and a review of these 
processes can serve only to increase our admiration for the precision 
and facility with which the chemical operations of the living body are 
conducted. Regarding for the sake of simplicity only the purine 
nucleotides, these are probably the first products of hydrolysing nucleic 
acid, and from them there may be liberated either phosphoric acid 
by a phospho-nuclease, or the purine-base by a purine-nuclease, giving 
rise to guanine and adenine, with their nucleosides, guanosine and 
adenosine. Thereafter the procedure is less obscure. The four pro- 
ducts exchange their amino-group for hydroxyl under the influence of 
their respective deaminase—namely, guanase, adenase, guanosine- 
deaminase or adenosine-deaminase. The two original nucleosides, with 
their corresponding derivatives, xanthosine and inosine, are then 
hydrolysed by their appropriate hydrolase, and the resulting oxypurines, 
xanthine and hypoxanthine, are further oxidised by xanthine-oxidase 
to uric acid. This is the concluding phase of purine metabolism in 
man and apes, but other animals are able to transform uric acid into 
allantoin by means of uricase. The changes may be represented 
diagrammatically as follows :— 
Nucleic Acid 
| 
3 mae 
Guanosine Adenosine 
Guanine | | Adenine 
y \ | 
Xanthosine Tnosine 
Te, 7 2 aabaalysp 
i <- 
\ 
Dyie! Acid — A ____________________ +5 allantoin 
Considerable progress has been made also in localising the various 
enzymes among the organs of the body, particularly those of animals. 
Into the results of these inquiries it is not the purpose of this address 
to enter further than to indicate that they reveal a marvellous distribu- 
tion, throughout the organism, of materials able to exert at the proper 
moment those chemical activities appropriate to the changes which 
they are required to effect. The contemplation of such a system 
1921 F 
eS By poxantnine 
