On the other hand, the lower end, which rests within the Cricoid ring and which was likely to be forced against the mucous membrane of the trachea occasionally, was somewhat thickened to avoid the friction and leverage that might be exerted if there were any free-play allowed.
"Makers of Modern Medicine"
James J. Walsh
Anatomically, there is such a weak spot in the posterior wall opposite the Cricoid cartilage, known as the pharyngeal dimple, between the circular and oblique fibres of the crico-pharyngeus muscle.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson
The sterno-hyoids and sterno-thyreoids are separated; the cross branch between the anterior jugular veins, and any other veins met with, secured with forceps before being divided; and the trachea exposed by dividing transversely the layer of deep fascia which passes from the Cricoid to the isthmus of the thyreoid.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson