SECTIONAL TRANSACTIONS.—J. 539 
and there is no consciousness of trunk muscle response. If ineffective, get 
diaphragmatic tug (e.g. in lift). Co-ordinate response involves accurate 
abdominal muscle contraction to balance g and, if this has to be maintained, 
a change from diaphragmatic to costal breathing. With incoordinate 
response diaphragm works against rigid belly wall, the abdominal contents 
are squeezed as in vomiting, and if this persists the whole nausea-vomiting 
cycle is evoked. In the other type there is a general rigidity of limbs and 
trunk in an exaggerated and incoordinate effort to prevent displacement of 
the body. This includes rigidity of abdominal muscles, and so the same 
result ensues. 
Flight-Lt. J. A. G. Hasta. 
Experiences from flying relating to the subjects of the discussion ; these 
will illustrate some of the points in Dr. MacCurdy’s paper (q.v.). 
Dr. T. G. MaITLanp. 
Rectilinear movement as a cause of general vertigo— 
The relation of general vertigo to special vertigo in so far as they both 
result from passive displacement. Among modern forms of locomotion 
the best example of displacement causing general vertigo is the swift vertical 
drop in a lift, and of that causing special vertigo the flat spin of an aeroplane. 
Under which category do the movements of swings, switchbacks, of 
aeroplanes passing through air pockets, of boats in a rough sea, fall? All 
these movements have angular direction, but the resulting vertigo is general 
rather than special, which implies the activity of a rectilinear factor. 
What, then, is the relation of the semicircular canals to rectilinear move- 
ment? 
The reactions, both physiological and psychological, associated with general 
vertigo would seem to demand another receptor. 
The interpretation of vertigo and its biological significance. 
Sq.-Leader E. D. Dickson. 
Mr. R. J. BARTLETT. 
Insufficiency of oxygen supply in brain owing to faulty breathing as 
a cause. Disequilibrium not essential. In air and water travel dis- 
equilibrium possibly a principal cause of faulty breathing. Train and 
motor sickness not readily so explained. Partly explained by somatic 
reactions to variations in speed. Complaints of vibration and noise. 
Noise investigation results stress psychological factors. Some Effects of 
Low Frequency Vibration on Body and Mind reported in 1930. ‘ Giddiness,’ 
* dizziness,’ ‘ dullness,’ ‘ sleepiness ’ and ‘ intense cold ’ induced by vibra- 
tion. Accompanying pneumograph records show shallow, fluttering or 
panting breathing punctuated with deep gasps. The pulse also affected. 
Mechanical vibration not essential. A ticking metronome induces 
changes in breathing of susceptible subjects. As metronome rate changes 
breathing changes in sympathy until it becomés impossible to change 
further, when there is great discomfort until subjective metronome rhythm 
changes to one with which breathing can harmonise. ‘ Torture’ due to 
the ‘ drip-drip ’ of water similar. Record of a case in which the water- 
dripping frequency was slowing down and passed through the pulse rate. 
External physical causes not essential. Purely physiological causes 
