i 82 
THE ENERGY OF THE LIVING PROTOPLASM. 
The lateral chains of aromatic ketones are oxidised to carboxyl, 
if the benzene ring does not contain a hydroxyl-group, otherwise 
the entire compound will reappear in combination with sulphuric 
or glucuronic acid in the urine, with the lateral chain preserved 
( Nencki ). Some sulphur compounds will yield sulphuric acid, 
while others will not. (I) 
It is, further, of great interest that the oxidation of benzene 
to phenol and to small quantities of pyrocatechin and hydro- 
quinone in the animal body (Nencki and Giacosa) is diminished by 
the introduction of certain poisons. (2) 
The difficulty in completely oxidising benzene derivatives of 
a certain constitution is not only encountered in the animal but 
also in the vegetal organism. Many plants accumulate tannins 
and related compounds without ever utilising them again ; in 
most cases they are excreted and may by their repulsive taste 
prevent depredations by various animals : only under certain 
conditions may tannin be utilised again. (3) Also certain alkaloids 
in plants undergo no further metamorphosis (4) and have to be 
looked upon as excreta. It is, further, very characteristic of 
the oxidising faculties of plant-cells that certain compounds are 
left unchanged, which, even by such a comparatively weak 
oxidising agent as hydrogen peroxide, are attacked readily. Thus, 
it was observed by Pfeffer that cyanin (a quinoline derivative), 
introduced into plant-cells is not altered, while it is easily bleached 
by the peroxide. Also certain compounds in the roots of Vicia 
and of Trianea Bogotensis are easily converted into brown oxida- 
(1) Compounds of the general formula NH2—CO—S—R easily yield sulphuric 
acid ; thiophen or sulphonal do not (Smith). 
(2) Nencki and Sieber (Pflüg. Arch. 31, 319). found, e.g., that while in the body 
of a healthy man 0.82 g. phenol was formed from 2 gram benzene, under normal 
conditions, only 0.33 g. was formed if 2 gr. ethyl alcohol per kilo of body-weight were 
administered at the same time. Also individual differences were noticed. Poisons 
may also interfere with normal oxidising processes; thus, diamide in non-lethal doses 
leads to the appearance of allantoin in the urine of dogs (Borisson, Z. physiol. Chem., 
19 , 499 ). 
(3) Small kinds of Spirogyra will use up their tannin after a few weeks cultiva¬ 
tion in a solution containing 0.5 o/ 0 KH2 PO4 ; 0.2 o j 0 KH C 0 3 and traces of nitrate 
and sulphate of calcium. 
(4) Cf. the investigations of Leo Errera , Maistriau, and Clautriau, especially 
those of the latter in the Bulletin Belge de Microscopie, 1894. 
