IIO ANIMAL CHEMISTRY LECTUEE Y. 



special examination. Hippuric acid we have already discussed 

 somewhat fully, while the consideration of uric acid I must 

 postpone to my next lecture. There remain, then, only leucine 

 and tyrosine ; but, before adverting to the natural occurrence 

 of these bodies in the living and dead body, let me direct your 

 attention for a short time to certain allied products obtainable 

 from nitrogenous tissue by artificial processes. 



(117.) When flesh, for instance, is submitted to the action of 

 the oxidising agent most commonly employed by chemists 

 namely, a mixture of sulphuric acid with either bichromate of 

 potassium, or peroxide of manganese there are produced a con- 

 siderable number of monobasic acids, to which I shall refer more 

 particularly hereafter, together with several of their associated 

 aldehydes and nitriles. Now the relationship of an aldehyd to 

 its corresponding acid and alcohol is very simple, and may be 

 exemplified by common or vinic aldehyd among fatty, and by 

 benzoic aldehyd among aromatic compounds. Thus, when vinic 

 alcohol is submitted td oxidation, it does not simply take up an 

 additional dose of oxygen, but instead gives up a portion of its 

 hydrogen to the oxgenant, being thereby converted into alcohol 

 dehydroffenatus or aldehyd, thus : 



Alcohol Oxygen Water Aldehyd 



C 3 H 6 + = H,0 + C a H 4 



The resulting aldehyd is a much more readily oxidisable substance 

 than the original alcohol, and upon exposure to air, is rapidly con- 

 verted by direct absorption of oxygen into acetic acid, thus : 



Aldehyd Oxygen Acetic acid 



C^H 4 + C 2 H 4 2 



Similarly, benzyl-alcohol is not susceptible of mere oxidation, but, 

 by the action of oxygenants, is dehydrogenised into benz-aldehyd, 

 or essential oil of bitter almonds, 



Benzyl-alcohol Oxygen Water Benz-aldehyd 



C 7 H 8 -f = H a O + C 7 H 6 



