OF THE CENTRAL MOTOR INNERVATION OF THE LARYNX. 
195 
the excitability of the bulbar centres when these were cle})ressecl by shock, 
exposure, &c. 
In every case a post-mortem examination was made, the drawings verified and the 
specimen preserved. 
d. Iiijiuence of the Amesthetic and Strength of Stimulus. 
We have assumed that the construction of the whole neuro-muscular apparatus of 
the larynx comprises (1) an area of cortex popularly, though incorrectly, termed the 
cortical laryngeal centre, (2) a similar area in the bulb or medulla oblongata which 
may in like manner be spoken of as the bulbar laryngeal centre and is connected 
with the cortical apparatus by fibres running in the corona radiata and internal 
capsule, while finally the vago-accessory nerve roots and peripheral branches contain 
the fibres supplying the laryngeal muscles and mucous membrane. 
It was first observed by Hooter* that even when the recurrent nerves were cut 
inhalation of large doses of ether produced paralysis of the closers (the adductors) of 
the glottis before the openers (the abductors). We repeated! and extended in further 
detail this observation and showed that this remarkable peripheral and differential 
action of etlier was, in all probability, due to the fact that the antagonistic muscles of 
the larynx belong to classes of muscles biologically different. 
Hooper’s original observation was contested by Donaldson, j who found that in 
certain cases one of the two groups of muscles predominated according to the strength 
of the stimulus, that with a feeble current, opening, with a strong current, closing, of 
the glottis was produced. A further, later research by Hooper§ showed that the same 
effect is produced by vaiying the rate (i.e., the intensity ?) of the stimuli, with a slow 
rate of interruption of a constant current abduction being obtained, with a quick 
rate adduction. 
We have observed Donaldson’s result to be occasionally jR'esent, and from general 
considerations are ready to believe that Hooper’s second observation is correct. It is 
clear that the ether effect, and the intensity of stimulation effect mutually confirm 
each other. All these results apply in their entirety to Dogs only. Both, however, 
have to be kept in view when considering the results of exciting, as in the present 
research, the highest point of the effei’ent neuro-muscular track of the laryngeal 
apparatus in any animal, since it is obvious that the actual representation of move¬ 
ment (whether closure or opening of the glottis) might be masked by the condition 
of the peripheral mechanism ; for instance, if this were poisoned with ether stimu¬ 
lation would give opening only of the glottis. 
* ‘Transactions of the American Laryngological Association,’ voh 7, 1886. 
t ‘ Brit. Med. Journal,’ 4-11 September, 1886. Vide also Biedermaxn, ‘ Centralblatt fiir Physiologic,’ 
and Bowditch, ‘International Journal of the Medical Sciences,’ April, 1887, p. 444. 
X ‘American Journal of Medical Sciences,’ July, 1886. 
§ ‘ Transactions of ihe American Laryngological Association,’ 1888. 
2 c 2 
