Bawden, Nose and Jacobsoris Organ. 123 



primitive establishment of cerebral connections, is the sense of 

 smell. As Edinger says: "We are today justified in assuming 

 that the cortex is the bearer of the higher psychical functions. 

 If then it is true that the olfactory tract connects with the 

 higher centers first in phylogenetic development, then it follows 

 that the earliest cortical activity is associated with the percep- 

 tions of smell." What the ultimate significance of the early 

 development of the olfactory sense may be, is yet to be deter- 

 mined. 



With regard to the delicacy of the sense of smell even in the 

 higher types where it is not so fine a sense, it has been shown 

 by experiment that 4))U ,uuu,uuo P art °f a milligram of polycarpine, 

 ° r •3011,000 P art °f a milligram of bromine, in one square centi- 

 meter of air is perceptible. Olfactory sensations are probably 

 received from material emanations from the odoriferous sub- 

 stance, the emanations being absorbed by the fluid in which the 

 end-cells are imbathed. This moisture is so essential to the 

 proper action of these cells that its absence, as in certain stages 

 of a cold and in certain diseases, may for the time quite destroy 

 the sense of smell. For the same reason odors are less readily 

 perceived in an uncommonly dry atmosphere. This blunting of 

 the sense is brought about also by certain occupations which 

 necessitate working in a dusty atmosphere. 



The nerves of smell may become the seat of disease. An 

 abnormal increase of the acuteness of the olfactory sense is 

 hyperosmia ; an abnormal decrease, anosmia. Complete abolition 

 of the sense sometimes takes place. It seems that for the de- 

 velopment of smell the odorous particles must be transmitted 

 to the nasal mucous membrane in a gaseous medium as the 

 simultaneous contact of fluids destroys all appreciation of odor. 

 Section of the olfactory bulbs entirely destroys the sense of 

 smell. Injury to the fifth nerve may also destroy smell even 

 where the olfactory nerve remains intact. This is probably only 

 an indirect cause, however. This may be plausibly explained 

 as the result of a deficiency in the secretion which is controlled 

 by this nerve branch. 



The delicacy of the sense of smell is determined in experi- 



