Dr Stark on the Influence of Colour on Odours. 85 



the less true that they do exist.* It is by means of this special 

 odour, this individual atmosphere, that the dog follows the traces 

 of wild animals hours after they have passed ; and it is by this 

 that the same animal is enabled to iind the track of his master, 

 and to distinguish him at once among a thousand individuals. 



Further, besides the odours or emanations of health, there 

 exist particular odours, characteristic of animal bodies in a state 

 of deranged action or disease. Thus in fever, small-pox, and 

 other eruptive diseases, a particular odour is exhaled from the 

 patient, typical of the affection ; and this, in many cases, is so 

 well marked, that the nature of the ailment may often be dis- 

 tinguished by the odour alone. The particular emanation which 

 arises in the ill-ventilated and often crowded apartments of the 

 poorer classes of society, and in prisons, is well known, when 

 concentrated, to be extremely dangerous ; and modifications of 

 this and similar effluvia, when more attention shall be directed 

 to the subject, may often afford the physician an indication of 

 lurking disease. 



The remarkable diffusion of odorous particles through the 

 air, without the odorous body adding perceptible weight to the 

 medium by which it is communicated, was observed by the cele- 

 brated Mr Boyle. This philosopher had turned his attention 

 to odours, or effluviums^ as he has termed them, and made ex- 

 periments on certain odorous bodies, which are detailed in his 

 essay on " the strange subtilty of effluviums.*" This sagacious 

 experimenter, and almost the only writer on the subject previous 

 to Cloquet in 1815, treats the subject of effluviums under the 

 following heads : — " 1. The strange extensibility of some bodies 

 while their parts remain tangible. 2. The multitude of visible 

 corpuscles that may be afforded by a small portion of matter. 

 3. The smallness of the pores at which the effluvia of some bo- 

 dies will get in. 4. The small decrement of bulk or weight that 



• " Les habitans du Quercy et du Rouergue se nourissent de froment, 

 d'oignons, d'ail, et boivent habituellement du vin. Ceux de la Haute-Au- 

 vergne ne vivent au contraire que de lait, de fromage, de seigle, de sarrasin, 

 et ne boivent que de Teau. Lorsque la saisou des moissons rassemble ces 

 peuples dans un meme canton, on distingue facilement les Quercinois et les 

 Rouergats k I'odeur fetide et ammoniacale qu'ils repandent autour d'eux, 

 tandis que celle des Auvergnats rappelle le pelit-lait aigri et tournant ^ la 

 putrefaction." — Osphresiologie^ p. 65. 



