[Ossification principle of the laryngeal skeleton of the human and mammals. Comparative anatomic studies]

In 3 oxen, 24 deer, 40 common hares and 27 rabbits, the laryngeal cartilages, freed from soft tissue, were examined roentgenologically for ossification, and compared with the well-known ossification pattern of the human thyroid cartilage. In the human, the thyroid cartilage ossifies in four preferential directions: horizontal-caudal, vertical-lateral, vertical-median, and obliquely tongue-shaped; in cattle ossification in the three directions: horizontal-caudal, vertical-median, and vertical-lateral; and in the deer in two directions: median-concentric and vertical-lateral. The cricoid cartilage in cattle and deer ossifies at the lamina and the upper border of the arch, the arytenoid cartilages ossify at the muscular process. In the common hare the thyroid cartilage ossifies only rarely, the other cartilages, in common with the entire laryngeal skeleton of the rabbit, never. The cause of ossification of the laryngeal cartilages is their deformation by the muscles of the larynx. The differences in the ossification patterns in humans, cattle and deer are due to the species-specific mechanical stress determined by the respective anatomy. The absence of ossification in the common hare and rabbit, on the other hand, is an expression of too small a deformational stress of their laryngeal skeleton. Ossification and nonossification are examples of the same principle, the self-regulating adaptation of connective and supportive tissues to mechanical stresses.