178 Professor William Stirling [May 12, 



Equilibration and ^'■The Acrobatic Frog.'''' 



The mechanism for the maintenance of the equilibrium of the 

 body is one of the most complex in static physiology. Many factors 

 are concerned in this process, including the impulses sent from the 

 semi-circular canals. The late Prof. Goltz, many years ago, removed 

 the cerebral lobes from a frog, all in front of a line joining the fore- 

 most margin of the exposed tympanic membranes. Such a frog, if 

 placed on a horizontal surface, sits, but does not move ; if placed on 

 its back, it immediately " rights " itself. If, however, the board on 

 which it is sitting be slightly tilted, the frog moves upward on the 

 board ; and if the board be rotated, the frog still continues to move 

 onward ; and when the board is vertical, the frog rests and sits or 

 perches quiescent on the edge of the board. As soon as the board is 

 again tilted, the frog moves correspondingly, and one can make it 

 crawl up and round the board as often as one chooses by simply 

 turning the board on its long axis. I have called this " The Acro- 

 batic Frog." An intact frog does not behave in this way. When 

 the board is tilted, it jumps, while one with its spinal cord only, falls 

 as soon as the board is sufficiently tilted ; nor does such a frog right 

 itself to the sitting position when it is placed on its back. 



Breathing and Artificial Inflation of the Lungs. 



The lungs as they appear in a dead rabbit after the chest is 

 opened were shown, and then the rhythmical filling and partial 

 emptying of the elastic lungs when artificial respiration or inflation 

 of the lungs is performed through a cannula placed in the wind-pipe, 

 an experiment well calculated to show the collapse of the lungs when 

 the chest is opened, as well as the elastic properties of the lungs 

 themselves. 



X-Rays and Movements of the Intestinal Tube. 



The movements of swallowing food mixed with subnitrate of 

 bismuth — which is opaque to X-rays — the j)assage of the food from 

 the gullet into the stomach, and from the stomach into the intestine, 

 were made visible by means of a film prepared by M. Carvalho. The 

 film was obtained from a frog which had been fed with bismuth 

 mixture. The contractions of the intestinal tube propelling onwards 

 its contents could be followed with the utmost distinctness. 



The Heart Beating. Arrest of the Heat. 



A series of films was projected to show the beating of the heart 

 in situ in a dead frog. Alongside it was shown the lever of a time- 

 marker indicating seconds. The arrest of the beat of the frog's heart 

 by electrical stimulation of an appropriate area of the heart itself, or 

 the branch of the vagus nerve passing to the heart, was shown, as 



