902 REPORT—1899, 
TUESDAY, SEPTEMBER 19. 
The following Papers were read :— 
1. The Dependence of the Tonus of the Muscles of the Bladder in Rabbits on 
the Spinal Cord. By Joun P. Arnowp, Philadelphia. [From the 
Physiological Institute of the University of Bern.| 
I. The tonus of the Sphincter is normally greater than that of the Detrusor. 
1. The Sphincter may be so strongly contracted as to withstand, at first, a water 
pressure of 68°2cm. In other cases it may only withstand a pressure of 17 cm. 
2. The Detrusor tonus in a moderately filled bladder, soon after catheterisation, 
may be as high as 31'4 em. water pressure. On the other hand the tonus of the 
Detrusor in a moderately filled bladder may be as low as 3°5 cm. 
3. Normally the Sphincter tonus remains tolerably constant between 25 cm. 
and 30 cm., but may vary between 31 cm. and 38:2 cm., as observed in one 
rabbit, or between 17 cm. and 24 cm. as observed in another. 
4. The tonus of the moderately filled bladder is normally between 4 cm. and 
5 ecm. water pressure. The tension rises in proportion to the fulness. 
5. Under high pressure both the Sphincter and the Detrusor make rhythmic 
contractions at irregular intervals. 
II, After shutting off the blood supply from the lower part of the spinal cord 
by compression or ligation of the abdominal aorta, the tonus of the Sphincter and 
of the Detrusor sinks rapidly. 
1. The tonus of the Sphincter falls at once very rapidly, quite low, then 
gradually, until all tonus is lost. In one animal the tonus of the Sphineter did 
not begin to fall until twelve minutes after ligation of the aorta. In this case the 
aorta was ligated just above its division. 
2. The Sphincter may still retain a small degree of tonus as long as 14 hour 
after death. 
3. The tonus of the Detrusor falls more slowly than that of the Sphincter. 
4. In one experiment we observed, after swallowing movements produced by 
stimulation of both superior laryngeal nerves, a rapid sinking of the Sphincter 
tonus. 
5. Physical disturbances, such as loud noises, lower the tonus of the Sphincter. 
In our experiments normal salt solution, kept at a constant temperature between 
39° and 41° C., was used in the bladder. Before passing the catheter the penis 
was rendered anesthetic by a 5 per cent. solution of cocain. 
Animals which were killed by bleeding or by section between the medulla 
and cerebellum gave similar results to those observed after ligation or compression 
of the aorta. After section above the medulla artificial respiration was used. 
During this period the Sphincter tonus fell more slowly. 
2. Observations on Visual Acuity from Torres Straits. 
By Dr. W. H. R. Rivers.—See Reports, p. 586. 
3. Observations on Visual Acuity from New Guinea. 
By C. G. SELIGMANN. 
4. On a New Instrument for measuring the duration of Persistence of 
Vision on the Human Retina. By Eric Sruart Bruce, M.A.Ozxon., 
F.R.Met.Soc. 
The aerial graphoscope devised by the author for measuring the duration of 
persistence of vision on the retina consists of a lath of wood 76 centimetres long 
