On each side of the thyroid cartilage we can recognise the lateral lobes of the thyroid gland. On the upper and front part of the gland we can distinctly feel the pulsation of the superior thyroid artery. This pulsation, coupled with the fact that the gland rises and falls with the larynx in deglutition, gives the best means of distinguishing a bronchocele from other tumours resembling it. Below the angle of the thyroid cartilage we feel the interval between it and the cricoid, which is occupied by the cricothyroid membrane. In laryngotomy we cut through this membrane transversely close to the upper edge of the cricoid cartilage, in order that the incision may be as far as possible from the attachment of the vocal cords. 25. =Cricoid cartilage.=--The projection of the cricoid cartilage is a point of great interest to the surgeon, because it is his chief guide in opening the air-passages, and can always be felt even in infants, however young or fat. It corresponds to the interval between the fifth and sixth cervical vertebræ. The commencement of the œsophagus lies behind it: here, therefore, a foreign substance too large to be swallowed would probably lodge, and might be felt externally. Again, a transverse line drawn from the cricoid cartilage horizontally across the neck would pass over the spot where the omo-hyoid crosses the common carotid. Just above this spot is the most convenient place for tying the artery. 26. Those who have not directed their attention to the subject are hardly aware what a little distance there is between the cricoid cartilage and the upper part of the sternum. In a person of the average height sitting with the neck in an easy position, the distance is barely one inch and a half. When the neck is well stretched, about three-quarters of an inch more is gained. Thus, we have (generally) not more than seven or eight rings of the trachea above the sternum. None of these rings can be felt externally. The second, third, and fourth are covered by the isthmus of the thyroid gland. The trachea, it should be remembered, recedes from the surface more and more as it descends, so that, just above the sternum in a short fat-necked adult, the front of the trachea would be quite one inch and a half from the skin.