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.
View full abstract