142 On Excitation of the Floor of the tli Ventricle. [June 18, 



carrying out this research ; and also to Professor T ait for allowing 

 us the use of his laboratory and his valuable apparatus, without 

 which these results could not have been obtained. 



VIII. " On the Changes evoked in the Circulation and Respira- 

 tion by Electrical Excitation of the Floor of the 4th Ven- 

 tricle." By W. G. SPENCER, M.S., Assistant- Surgeon to 

 the Westminster Hospital. Communicated by Professor 

 HORSLEY, F.R.S. Received June 15, 1891. 

 (Abstract.) 



The object of the research was to connect more closely clinical 

 signs with pathological changes in the medulla by localising in the 

 floor of the 4th ventricle the " centres " which influence the circula- 

 tion and respir ition. 



The author commences his paper with a full account of the work 

 of previous observers upon the medulla in relation to the circulation 

 and respiration. 



The research differs from preceding ones in the use of the electric 

 current to excite without injury the floor of the ventricle, in avoiding 

 puncture and incision of the medulla, in employing complete 

 anaesthesia with ether without at the same time impeding respiration. 



The floor of the 4fch ventricle was accurately measured in each 

 experiment, so that the distance from the calamus scriptorins and 

 from the middle line of each point was known before it was excited. 

 The experiments were performed on cats, dogs, and monkeys, the 

 records of the changes which took place being divided into those 

 affecting respiration, the rate of the heart, and the blood-pressure 

 respectively. 



By adding together the results obtained for each point in all the 

 experiments on animals of the same species, conclusions have been 

 arrived at for each species, and a comparison is then made of the 

 three species of animals. 



The conclusions drawn from the experiments, aided by the facts 

 detailed in the historical retrospect, are as follows : 



(1.) Inspiration. The part of the floor of the 4th ventricle which, 

 when excited, caused an increase in the normal inspiratory 

 impulses descending to the thorax lies along the middle line, 

 extending for 2 mm. on either side. 



(2.) Expiration. The part of the floor of the 4th ventricle which, 

 when excited, caused an increase in the normal expiratory 

 impulses descending to the thorax lies along the lateral part 

 of the ventricle, 2 to 3 mm. from the middle line. 



