— io; — 



size of the contact-surface, i. e. the pushed out length of the cylinder, 

 and can be determined from the composition of the gaseous, and the 

 rapidity of evaporation of the liquid phase. In this manner odori- 

 metry, designed in the first instance as an indirect method, now devel- 

 ops into a direct one. It shows us at once the quantity of odorous 

 substance which must be added to the unit of volume of inhaled air 

 in order to produce a sensation of smell; but this would only be of 

 importance for odorimetry in itself, if the measure of olfactive energy 

 which is just sufficient for exciting the sense-organ, could be measured. 



A further examination deals with the subject of „ tasting by 

 smell" 1 ), an occurrence which is especially clearly noticeable in the 

 form of a sweet taste, which can be brought about by the odour of 

 chloroform. Zwaardemaker believes that the seat of this excitement 

 of the sense may be localised in the epithelial buds recently discovered 

 in the regio olfactaria of mammals. By means of olfactometric 

 measurements it was found that the limit of excitement of the odour- 

 sensation requires 2,6 mg. chloroform in 1 litre air, that of the taste- 

 sensation 13,0 mg. 



Of particular interest is a treatise on the „sensation ofinodor- 

 ousness" 2 ). 



Absolutely inodorous surroundings are in Zwaardemaker's opinion, 

 like an absolutely dark and noiseless space, of rare occurrence, as 

 almost every substance possesses its specific odour. The fact that 

 we do not usually perceive it, depends, apart from our carelessness, 

 upon the ventilation which enfeebles the odour, and, perhaps more 

 correctly, produces transitions. If, therefore, we desire to become 

 acquainted with the sensation of inodorousness, we have generally to 

 resort to an intentionally produced state of inodorousness. The most 

 suitable arrangement for this purpose is a glass case of 40 cc. capa- 

 city with an opening for the nose. If this case is carefully freed from 

 adhering odours, the air contained in it will be found nearly odourless. 



A different kind of inodorousness which is more often realised, 

 consists of the compensation of odours which supplant each other. 

 A complete compensation, however, occurs only in the case of very 

 faint odours, whilst powerful excitants enter into a contest with one 

 another. A difference between the sensation of this apparent inodor- 

 ousness and the actual one does not exist. Zwaardemaker also 

 considers a third kind of inodorousness possible. Concentrated solu- 

 tions of many odorous substances, as compared with dilute ones, have 

 a remarkably faint odour. On repeated observation it becomes more 

 and more faint, and finally disappears almost completely. It is not 



1 ) Arch. f. Anatomie und Physiologie 1903, 120. 



2 ) Untersuchungen aus dem physiologischen Laboratorium 5. Series IV, II. 



