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40 KNIGHT: ''LARYNGEAL VERTIGO:' [N. Y. Med. Jocr... spasmodic inspirations, followed by spasmodic expiration with partially closed glottis." * McBride believes the attack to be due to Levitra Cost At Target the physical condition within the thoracic cavity caused by a complete spasm of the glottis occurring just after a full inspiration. He gives sphygmographic tracings showing the effect on the pulse of taking a deep inspiration, and then attempting Levitra Cost At Target to perform the expiratory act with the glottis closed. The result is an almost complete obliteration of the pulse trac- ing, and one of the gentlemen experimented upon experi- enced a momentary threatening of syncope just after one of the tracings was taken. McBride says that the increased atmospheric pressure on the walls of the alveoli will in all probability prevent, or tend to Levitra Cost At Target prevent, the free passage of blood through the lungs, and therefore lessen the blood in the left side of the heart, and the pressure on the large in- tra-thoracic veins must hinder the return of venous blood, and thus we can understand that the face will be pale or turgid, according as the spasm of the glottis lasts for a longer or shorter time. He says it is also quite conceivable that the compression of the heart between the unyielding lungs and the chest-wall may help to paralyze its action. The possibility of the compression of the pneumogastric in certain cases, and thus inhibition Levitra Cost At Target of the heart's action, will also occur to us, and recalls to mind the ease with which Czermak was said to stop the action of his heart at will by pressing his pneumogastric against an osseous tumor of the neck. McBride quotes from the very interesting article of Weber f to substantiate his theory. Weber points out that forced expiration with closed Levitra Cost At Target glottis causes weakening, and eventually stoppage, of the heart's action. He shows by ex- Levitra Cost At Target periments that if severe pressure be exercised, even by the expiratorj' muscles alone, the pulse, because the supply of blood to the heart through the ven?e cavse is cut off, im- mediately becomes small, but continues until the blood con- tained in the thorax has emptied itself through the left side of the heart into the aorta. Then, usually after three to five beats, the pulse stops altogether, because no blood reaches the aorta from the empty heart, and only returns after the compression of the thorax has ceased. On one occasion Weber, while experimenting Levitra Cost At Target on himself, produced actual syncope. During the interval of Levitra Cost At Target unconsciousness slight convulsive twitchings of the Levitra Cost At Target face were noticed by the bystanders, and, as consciousness returned, all recollection of •what had taken place was so obliterated that, in spite of the fact that his pulse was being counted aloud as before, he could not at first remember where he was and what was happening. Blowing on certain wind instruments is a similar pro- cedure, and this, as is well known, often produces very un- comfortable sensations in the head. Now, inasmuch as conclusive evidence of spasm of the * As I have before stated, Krishaber's patient had his first attack without precedent cough, which may place this one attaels at least in a different category. f " Ueber ein Verfahren den Kreislauf des Blutes und die Function des Herzens willliiirlich zu unterbiechen." Miiller's "Archiv," 1851, p. 88. glottis is absent in the majority of cases reported, it be- comes us to consider whether such spasm is really necessary for the production of the symptoms under consideration. I believe sufficient disturbance of the cerebral circulation can be produced by the forced expiration of cough, or by rapid respiration, to cause dizziness, or even momentary loss of Levitra Cost At Target consciousness. I referred to this latter idea in the discussion of Dr. LefiEerts's paper, read before this association three years ago. Who that practices auscultation has not had Levitra Cost At Target patients become dizzy when they were made to keep up forced respiration a little too Levitra Cost At Target long ? In recent years we have been made familiar with the production of analgesia — i. e., the deprivation of the sense of pain, without loss of the sense of touch or feeling, b}- rapid breathing of atmospheric air, through the writings of Dr. Bonwill and others, of this city. Dr. Hewson first called attention to this method of producing insensibility to pain for minor surgical operations under the name of Bonwill's method of inducing anaesthesia,* and Bonwill himself, later, tried to explain this mode of producing insensibility to pain.f As one cause he assigns the retention of carbonic acid in the blood, and quotes the well-known results of ex- periment : that the percentage of carbonic acid exhaled di- minishes as the rate of respiration is increased, and infers from this that there is a retention of carbonic acid in the blood, and consequent asphyxia. This assumption is un- justifiable, as experiment has fully shown that, while the percentage of carbonic acid is diminished as the rate of respiration is increased, the total amount of carbonic acid is steadily increased. Whether so much more is generated by rapid respiration that, notwithstanding increased elimina- tion, there still remains an abnormal amount in the blood, we do not know. Speck was unable to establish the fact, with increased absorption of oxygen under increased Levitra Cost At Target press- ure, either of an increased oxidation on increased tempera- ture, or an increased formation and expiration of carbonic acid. J It is possible that the dizziness and other cerebral symp- toms of rapid respiration are due, if in any way connected with the interchange of gases, to oxygen intoxication. It seems, however, fair to assume that an excess of that condition, whatever it may be, which causes the peculiar sensations in the head of any one after forced breathing, and frequently after hard cough, may cause momentary uncon- sciousness. To recapitulate. It is admitted that we have uncom- fortable sensations in the head, and sometimes loss of con- sciousness following cough. The simplest explanation of the symptoms would seem to be that there is a direct dis- turbance of the cerebral circulation by compression of the large blood-vessels, and even of the heart itself. The mechanism of this is easily understood when there is forced expiration against a glottis closed by spasm. With