TRANSACTIONS OF SECTION D. DBPT. ANATOMY AND PHYSIOLOGY. 717 



senses — muscular, optical, aud auditory. Those of the first two classes were fairly- 

 well known, the problems of the optical perception of space having been worked 

 ■out by Wheatstoue, Helmholtz, and others. The perceptions of space dependent 

 on the ear had been but imperfectly investigated. Theories had been put forward 

 and observations made by Anton, Steinhauser, Graham Bell, E. Mach, Lord 

 Rayleigh, Luca, Kupper,"'A. M. Mayer, and by himself. The author reviewed 

 various theories and observations which had been made. Steinhauser and Graham 

 Bell assumed the perception of direction to depend upon the relative intensity with 

 which a sound reached the two ears. Mach and Lord Rayleigh regarded the 

 perception as depending rather upon the relative differences of quality in the two 

 ears, these differences being due to the partial resolution of compound tones, 

 according to Mach, by reason of the ear-cavities acting as resonators, but according 

 to Lord Rayleigh by reason of diffi-action of the sound-waves around the head. 

 The author, in a paper on ' Binaural Audition,' read to this Section in 1878, had 

 shown that differences of phase were also of influence in the acoustic perception 

 of direction, The author also referred to a paper read by him before the Associa- 

 tion in 1879 on the Pseudophone, an instrument for investigating the laws of 

 binaural audition by the illusions it produces in the acoustic perception of space. 

 After discussing the merits of the various theories to account for the facts of 

 observation upon tones of different degrees of intensity, pitch, phase, and quality, 

 the author propounded the following theory : — ' Judgments as to the direction of 

 sounds are based in general upon the sensations of different intensity in the two 

 ears, but the perceived difference of intensity upon which a judgment is based is 

 not usually the difference in intensity of the lowest or fundamental tone of the 

 compound sound (or " clang "), but upon the difference in intensity of the individual 

 tone or tones of the clang for which the intensity-difference has the greatest 

 effective result on the quality of the sound.' The author concluded with some 

 remarks and suggestions as to the influence on the perception of sounds of the 

 form of the convolutions of the pinnae of the ears, and with the suggestion that 

 now that the physical bases of the problem had been laid down, the problems of 

 the acoustic perception of space would be greatly elucidated by experiments upon 

 persons possessed of abnormal hearing, and upon the blind, in whom this perception 

 is abnormally developed. 



■3. A Contribution to the Question on the Influence of Bacilli in the Pro- 

 duction of Disease. By Professor J. Cossar Ewart, M.D. 



About the end of March a new form of fever made its appearance in Aber- 

 deen. The fever began with the usual symptoms — there was a well-marked rigor, 

 then a sensation of coldness for some hours, accompanied with great depression, 

 the pulse was rapid, and the temperature steadily increased to 103, in some cases 

 to 105 deg. Fahrenheit. In the worst cases there was delirium. One of the most 

 characteristic symptoms was an affection of the deep cervical glands and lym- 

 phatics near the angle of the jaw ; the glands enlarged, and there was a feeling of 

 fulness about the throat, congestion of the tonsils, and pain along the course of the 

 lymphatics of the affected side of the neck. In from twenty-four to forty-eight hours 

 the fever subsided, leaving the patient in a very exhausted state. In most cases 

 there was a relapse which corresponded exactly with the first attack, with this 

 difference, that a different set of glands and lymphatics were affected. After this 

 relapse there was again apparent recovery and then a second relapse. In some cases 

 there were as many as six relapses, the relapses occun-ing regularly every second 

 day. In nearly all the cases recovery was slow, and in some abscesses formed near 

 the angle of the jaw. In three cases the disease proved fatal. When an inquiry was 

 instituted it was found that over 300 individuals had suffered from this disease, and 

 that all the sufferers had been using milk from the same dairy. A sample of milk 

 secured for examination, when the epidemic was at its height, was found to contain 

 numerous micrococci, fungi spores, and spores wliich resembled those of Bacillus 

 Anthracis — the organism which is associated with splenic fever. When cultivated 



