1922.] Sense 0/ Smell possessed hy Birds. 227 



marvellous than the stoop o£ a Falcon {Falco peregrinus) 

 on its prey, or the sharp vision of the Great Grey Shrike 

 (Lanius excuhitor), sometimes used in Holland for trapping 

 Falcons, and able to descry them at an incredible distance ? 

 But there are many birds besides Shrikes which can detect 

 an enemy soaring so high in the heavens that to the human 

 eye it is invisible, or only just within the extreme range of a 

 telescope. Another factor is that many — possibly most — birds 

 are provided with an extraordinarily delicate sense of hearing, 

 which, although it may not help in finding food, is constantly 

 warning them of danger. Ao;ain, the investigator has to be 

 cautious not to confuse the organ of scent with that of touch, 

 by means of which some birds feed — e. g., the Woodcock, 

 most of the surface-feeding Ducks, and (in part) the 

 Apteryx. Thus it will be seen what an involved business 

 it is for an experimenter to formulate any trial which appeals 

 to a bird's sense of smell, and which at the same time excludes 

 sight, hearing, and touch. 



If a bird smells food or scents the presence of enemies, 

 it does so by means of the olfactory nerve, for it is by this 

 small and delicate instrument, which passes from the nostrils 

 to the brain where it terminates in a bulb, that impressions 

 of odorous particles are conveyed. Chemical research tells 

 us that the agents which act upon this nerve, and thus give 

 rise to smell, are particles of effluvia, but of the extremest 

 tenuity, which animals can pick up with far greater celerity 

 than man. 



Unfortunately my knowledge of anatomy is of the smallest, 

 but Mr. R. H. Burne, who has been good enough to take an 

 interest in the present enquiry, has most kindly obliged 

 me with a photograph (PL I. figs. 1, la) of a section of an 

 Eaglets {Aqidla) head, which is preserved in the Museum of 

 the Royal College of Surgeons (Physiol. Series, No. E 119). 

 This is a help, and explanatory as showing in detail the 

 normal structure of the nose, olfactory bulb, and nerve ; 

 the left bulb and root of the left nerve are exhibited, and 

 the right nerve with its passage into the olfactory eminence 

 in the nose cavity. With this to aid, the position 



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