188 
DR. F. SEMON AND MR. V. HORSLEY ON AN INVESTIGATION 
organic disease those fibres are asnally primarily affected which are engaged in main¬ 
taining the automatic process of laryngeal respiration—seemed to indicate that there 
must be a central differentiation corresponding to these varied phenomena. Hence it 
was that the idea of the present research occurred to us. 
In planning such an investigation we naturally turn fit sc to the subject of the 
cortical representation of the larynx—a problem wltich, first touched upon by Ferrier 
and Duret, has been treated in detail by H. Krause at the instigation of H. Munk, 
and by Mastni. 
From this point we might proceed to the consideration of the fibres leading from 
the cortex to the lower centres in the medulla, as they pass through the corona 
radiata and the internal capsule. The investigation of these fibres by means of the 
excitation-method has, so far as we know, not been undertaken by any previous 
observer, thougli some work by the ablation and degeneration method has been 
performed by Krause. TTiis latter method and its cesults will be fully dealt with by 
us in a subsequent paper. 
Finally, we discuss the results of excitation of the central mechanism in the bulb, a 
branch of the subject which we commenced four years ago, and which also has not 
been treated, to our knowledge {confirmed by Professor Gad), by any previous 
observer. 
Before passing to a complete historical retrospect of the question, and before 
describing the method of our own experiments, we may state that, since we have 
forind certain important differences in the central structural arrangements in different 
species of animals, and also in animals of different ages belonging to the same species, 
it is essential that these should first be prominently and clearly expressed, in order 
that some discrepancies which exist in the statements of previous investigators and 
the classification of our own results might be properly understood. 
To the same category belongs the question of the action of anaesthetics upon the 
neuro-muscular system, a question the importance of which for the present investiga¬ 
tion can hardly be exaggerated ; since, for reasons which we will further discuss, the 
effect attained by exciting any given centre may be entirely modified by the mere 
degree of anaesthesia affecting the peripheral mechanism of nerve-endings and muscles. 
In a previous communication''^ we have shown the importance of the action of ether 
upon the peripheral nervous system, a factor which must be properly discounted in 
considering the action of the anaesthetic upon the nervous mechanism as a whole. 
These considerations of species, age, and anaesthesia will couipel us to further sub¬ 
divide the great groups into which we have arranged our facts. 
In the following historical retrospect of the results obtained by previous investiga¬ 
tors we have thought it best (to avoid misconception) to place each writer in the 
chronological order of the appearance of his publication. 
“ On an apparently peripheral and differential action of Ether upon the laryngeal mnscles,” ‘British 
Medical Journal,’ 1886. 
