282 MESSRS. F. GOTCH AND V. HOBSLEY 



kind, but it has the enormous disadvantage that it is impossible to alter the degree of 

 narcosis, and, as will be seen, such alteration is an essential condition in experiments 

 of the kind which we have undertaken. 



As regards the practical administration of the anaesthetic, the best results were 

 obtained by pushing the etherisation at first to a profound degree, so as to abolish 

 entirely superficial reflexes, and always by causing profound narcosis before per 

 forming any operation, such as division of the spinal cord, &c., which would, if the 

 narcosis were less deep, entail depressant effects upon the centres concerned with 

 systemic life through the damaging influence of shock. Subsequently when, the 

 operative procedure having terminated, the actual observations were being made, the 

 narcosis was rendered less and less intense as the slow collapse inseparable from the 

 experimentation asserted itself. This slow collapse, since it involves the gradual 

 failure in excitability of the nerve structures and primarily of the nerve centres, 

 has the same effect as an anaesthetic in producing narcosis, which was preferably 

 intensified by the administration of ether in small repeated doses rather than in few 

 large ones. 



SECTION II. OPERATIVE PROCEDURE. 

 1. Exposure of the Cortex and of the Corona Radiata. 



(A.) Cortex. The animal, having been deeply anaesthetised in the manner stated, 

 was further immobilised on a firm support, upon which a metal vessel was placed so 

 as to be underneath the thorax. This was kept filled with hot water and, combined 

 with suitable coverings for preventing loss by radiation, served to keep up the 

 temperature. 



The dura mater was then exposed lege artis to the necessary extent and over 

 the required region, all haemorrhage from the bone being instantly arrested by the 

 use of soft modelling wax, &c. As soon as the dura mater was cleared the wound 

 was closed, and kept covered with sponges soaked in hot 6 per cent, saline solution, 

 whilst the further operations necessary for the experiment were undertaken. 



The cortex was finally exposed by taking up the dura mater by means of iridectomy 

 forceps or fine curved needles, and dividing it, care being taken to keep it always 

 protected with hot saline sponges unless an actual experiment was in progress. 



(5.) Corona Radiata. The cortex having been thoroughly exposed, a sharp 

 scalpel was passed horizontally through the hemisphere in the plane of the centre of 

 the coronaT gyrus, and the upper and anterior thirds raised as a lid of a box. Pieces 

 of amadou were then gently laid and pressed on the edges of the cut, thus arresting 

 the free bleeding from the vessels of the pia mater. Care was always taken to 

 determine precisely the topography of the section, and to accurately apply the 

 electrodes to the fibres coming from the requisite area of the cortex. The necessity 



