:5S A N A T O M V A N D PHYSIOLOGY O F 



parts. During the spasm caused by the section of the spine, the expiratory mus- 

 cles, contracting, emptied the lungs, which were not again rilled with air. 



Experiment. — Turtle, weight 4 pounds. The sympathetic nerves' on both sides, 

 in this turtle, had been cut several weeks, and the wounds in the neck were nearly 

 healed. The animal seemed well and very active. The cervical spine was divided 

 with little loss of blood. General spasm ensued, the glottis opened, expiration 

 followed, but no after inspiration, and the glottis closed. During an hour no inspi- 

 ration occurred, although the glottis opened and shut at about the usual respiratory 

 intervals. To make more sure of this, the trachea was cut across, the lung fully 

 inflated, and a tube secured in the lower end of the trachea. Through a short 

 caoutchouc tube the trachea was thus connected with Poiseuille's ha?rnadynamometer, 

 rilled to its 0° with mercury ; on turning a stopcock the column rose about two milli- 

 metres, the glottis continuing in repose. Then the glottis opened, but no synchronous 

 contraction of the lung muscles took place; indeed, the slightest must have been 

 indicated instantly by the mercurial column. During frequent repetitions of glottic 

 motion, no correspondent activity was at any time exhibited by the respiratory 

 muscles of the breast-box. It follows, therefore, that while the flank respiratory 

 muscles may after separation from their nerve centres move for a time, as do other 

 habitually rhythmical muscles like the heart, that these motions do not occur in all 

 eases, and that they are plainly not dependent on a respiratory centre below the 

 line of spinal section. 



The regular movements of the glottis were, as we we have shown, uninterrupted 

 by the section of the cervical spine. The question arose as to the exciting cause 

 of these motions. That they were not due to impulses propagated through the 

 main trunks of the pneumogastric nerves, was shown by their continuance after the 

 successive division of these two nerves below the origin of the glottic nerves. It 

 thus became plain that the medulla must receive its excitations from the head alone, 

 perhaps through the fifth pair of nerves, which acted as afferent trunks, the motor 

 nerves of the larynx completing the nervous circle as efferent branches. Hence the 

 continued action of the glottis after division of the cervical spine. 



The principal points in the foregoing paper to which we desire to draw attention 

 as novelties are as follows : — 



1st. In Chelonians the superior laryngeal nerve is distributed both to the opening 

 and closing muscles of the glottis. 



'2d. The inferior laryngeal nerve is distributed solely to the opening muscle of the 

 glottis. 



3d. A true chiasm exists between the two superior laryngeal nerves. 



Mb. The expiratory muscle lies within the breast-box, and consists of anterior 

 and posterior bellies connected by a strong tendon continuous across the middle 

 line, and common to both sides of the animal. 



5th. The inspiratory muscles occupy the flank spaces on either side. 



6th. Inspiration is effected by the contraction of the flank muscles, which in 

 appearance strongly resemble the diaphragms of superior animals. 



7th. Expiration is effected by the consentaneous action of the four muscular 

 bellies above described, which thus compress the viscera against the lungs. The 



