640 ^^- HANS GADOW, 



the whole throat, the recoil will cause the cricoid and the upper 

 portion of the trachea to press upon the inside of the manubrium, 

 and tend to strain its two horns with the clavicles and the first ribs 

 asunder, in fact to produce an exaggerated „incisura jugularis manubrii". 



The considerable force, which a strained larynx can exhibit, needs 

 no fiirther comment than reference to a braying ass or a gurgling and 

 bellowing camel. 



However, since the howling apparatus begins to show itself already 

 in the erabryo whilst the two halves of the sternum are still separated, 

 and whilst the organs between head and ehest are still much crowded 

 together owing to the bent up position of the embryo, it is not im- 

 possible that the fissure of the manubrium has already originally been 

 acquired by the embryo itself, and has not been inherited. At any 

 rate the fissure is the secondary, the enlargement of the voice organs 

 the primary feature. An examination of the enormous bulla formed 

 by the basihyal bone and by the likewise extremely enlarged thyreoid 

 cartilage, can only be explained as resulting from the distention into 

 these parts of the blown out laryngeal sacs and similar recessus so 

 common in the Mamraalia. 



The various sacs of Mycetes have been described by Sir R. Owen 

 in his Anatomy of Vertebrates, vol. 3, p. 598. „From the forepart 

 of the Space between the upper and lower vocal cords the pair of 

 sacculi are developed, which line or occupy the thyreoid bulla, Be- 

 tween the glottis and the arytaenoid cartilages are the orifices of 

 a pair of pouches, continued rather from the pharyngeal than the 

 laryngeal membrane, which extend forward and upward on each side 

 of the epigiottis. From the upper part of the thyreoid sacculi are 

 continued a pair of pyramidal oval sacculi, which occupy the sides of 

 the interspace between the epigiottis and the hyoid; and from the 

 forepart of the thyreoid sac is continued the neck of the large infun- 

 dibular sac, which expands to occupy and line the huge bulla or bony 

 case formed by the basihyal." Similar laryngeal pouches occur in the 

 Great Apes and in other Oldworld Monkeys. According to Vrolik^) 

 they are larger in the males than in the females ; they grow with the 

 age of the animal and are consequently the largest in the most aged ; 

 they are dilatations of the ventriculi Morgagni in the Chimpanzee 

 and in the Orang-Utan, and sometimes reach far down on the neck, 



1) Vrolik, Article Quadrumana, in : Todd's Cyclopaedia of Anatomy 

 and Physiology. 



