The Saccus laryngis in PRIMATES

Abstract

From mcroscopic and microscopic observations on the laryngeal region, especially on the laryngeal air-sac (Saccus laryngis) of PRIMATES belonging to 9 families, 30 genera, 64 species, the following results were obtained (Table 1).
1) The Saccus laryngis and or Sacculus laryngis was found inside or outside the larynx in P RIMATES of all the 64 species (Table 3).
2) The Saccus laryngis were classified into 5 types, MSA, MIP, MIA, LS and VL, according to the distribution of their openings. In PROSIMII and Cebidae of ANTHROPOIDEA an intergeneric variation was observable in the opening types. In Cercopithecidae only 2 types of opening, MSA and VL, were found. In Cercopithecidae expect for Colobus the Saccus laryngis distributes outside the larynx only of type VL without any intergeneric variation. In Hylobatidae and Pongidae the Saccus laryngis is open at the opening of type VL.
3) The distribution of Saccus laryngis were classified into 6 types, (A), (B), (D), (E) and (F). In most cases of PROSIMII and the majority of Ceboidea of ANTHROPOIDEA, the Saccus laryngis distributes inside the larynx, which is type (F), or very small part of the Saccus laryngis distributes outside the larynx, which is (E) type. In Cercopithecidae and Hylobatidae of ANTHROPOIDEA the Saccus laryngis partially reaches the Regio pectoris anterior, which is (B), (C), (D) or (E) type according to the proportion of distribution outside the larynx. In Pongidae the largest part of the Saccus laryngis ditributes outside the larynx, which is (A) type.
4) Between Cebide and Cercopithecidae of ANTHROPOIDEA, the primary variation in the opening type appears, and the secondary variation from MSA to VL appears in Colobus of Cercopithecidae, the form of the opening, from which no variation in Saccus laryngis distributes outside the larynx, is considered to be related to the Systematical position of each family.
5) When the correlation between the distribution of Saccus laryngis and the body weight in Macaca is considered, the sexual difference in the size of Saccus laryngis is presumed to depend upon the difference in body size between the male and female which become distinct after the appearance of secondary sexual character.
6) The appearance of Saccus laryngis in PRIMATES is considered to result from their characteristic arboreal locomotion. This Saccus laryngis has been generally said to play a part in evolving them to erect bipedal walking, in other word, in releasing them from manual walking. It is considered, however, that in PRIMATES the difference in the opening type and or the distribution type are related to the difference in the locomotion behavior. For example, the type VL is related to the brachiation, and type MSA to the arboreal quadrupedlism. The variety of the opening type in PROSIMII and Ceboidea of ANTHROPOIDEA is considered to have some relation to the variety of their locomtion behavior.
7) In most PRIMATES the Sacculus laryngis exist separately without any relation to the opening of Saccus laryngis. In Hylobatidae and Pongidae this Sacculus laryngis vares into a specialization and become the Saccus laryngis whose distribution expands widely. The Sacculus laryngis of Hominidae is such an ordinary one as most of Non-human PRIMATES have.