105 - 
the eation- of “tie. a ee Tf, in quinol, the second hydrogen atom is likewise 
fixed, the odour is intensified. 
The carboxyl eroup directly combined with the nucleus is inodorous, but if a 
group is introduced between it and the nucleus, the body sometimes becomes strongly 
a odoriferous, such as with phenylacetic and cinnamic acids. Aliphatic substances, as is 
_ Known, likewise smell strongly. It is, therefore, in these cases not the hydroxyl group © 
- but the proximity to ee nucleus which, acting in a similar way as hydrogen, causes ~ 
-_ inodorousness. 
If the benzene nucleus is ortho- substituted, aromatics are obtained which belong - 
to a distinct class. Even quite different groups produce an odour, which distinctly 
indicates that they belong to this class; so, according to the author’s opinion, o-hydroxy- 
_ benzaldehyde (salicylaldehyde) and o-chlorophenol have a similar smell, and that of 
_ methyl salicylate (o-hydroxymethyl benzoate) would likewise point out the connection 
of this body with said class. Therefore, wherever the hydroxyl group in para position 
causes odourlessness, in ortho position it creates a determinate class of odour. 
_ The methoxyl group, found in almost every aromatic, is of great influence. 
Marchand resumes his views in the following sentences: — 
{. Aromatics are chemical substances which, in the main, contain an oxygen atom 
as linking atom. i 
2. A second hydroxyl or carboxyl oxygen atom in the same molecule greatly 
_ reduces the smelling power or destroys it altogether. 
3. The affinity of two oxygen atoms in the same molecule is neutralized by a CHs 
group in close vicinity, so that their inodorousness is likewise done away with. 
4. Strongly smelling bodies contain oxygen as a double-linked atom. 
5. The combination of two oxygen atoms, unfavourable for aromatics, is favourable — 
for disinfecting action. 
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In a treatise on the “Sense of smell and smelling substances in the animal king- 
dom” G. Rorig*) discusses the phenomena in animal life which have direct connection 
with their sense of smell or their own peculiar odour. It is not always necessary that 
animals be brought together in large numbers, as e. g. in zoological gardens, but very 
often the presence of one single animal suffices to make its own odour noticeable. 
_ So, a good many people smell at once when there is, or has been, a mouse in the 
room, and to others the smell of dog or a cat, of which some do not notice anything, 
is repulsive in the highest degree. 
The own peculiar smell and the sense of smell are, above all, means for main- 
taining genus; the former facilitates the meeting of individuals of the same genus and 
to preserve this, as well as, in special cases, to keep enemies away, whereas the latter 
has to examine the surrounding medium (air, water), to find food, to secure the return 
‘to the abode in case of leaving it temporarily, to discover enemies and, as the own 
smell; to promote the union of individuals of the same genus. It would be a mistake 
_to declare that those animals smelled the strongest themselves which have the keenest 
sense of smell. It would be more correct to say that animals with a keen sense of 
smell make the best use of it in their intercourse. The glands which secrete the 
smelling substances, by means of which the animals find one another, are frequently 
_ Situated only in a few parts of the body but are specially suitable for communicating 
the peculiar smell of the animals to their surroundings. In many cases the feet bear 
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4) Deutsche Parf.-Ztg. 2 (1916), 214. 
