Studies on the Respiration of the Silkworm.

(III) On the Air Current of Respiration

Abstract

1. This was studied on the gasdynamic relation of the tidal air to the respiratory organ.
2. The flow of the tidal air in the respiratory organ is considered as a laminar flow, the Reynolds number of which is small.
3. Unless there is excessive turbulence in the open air, the flow which is composed of radial stream lines seems to be arised in just outer side of the stigma, at this time the atmospheric pressure decreases as it approaches toward the stigma. The rate of decrease of the atmospheric pressure ∞1/(distance from stigma) ⁴and this is significant when the outside of the stigma is considered as the extension of the stigma.
4. The size of the angle (121.6°-178.9°) between two tangents drawn from the boundary portion between the peritreme and the sieve plate to the body surface around the stigma is inversely proportional to the size of stigma in most cases. This trumpet-shaped curvature seems to make the flow of the inspiration smooth and consequently increases the quantity of the inspiration. If the circumference of the stigma was angular, the air would not be able to change its direction smoothly because of its inertia even after it has already reached to the entrance.
5. At the boundary portion between the peritreme and the sieve plate, the velocity of the inspiration flow seems to be considerably fast, as the flow must move around the angle of 30°-40°.
6. According to the opening and closing of stigma, the velocity of the tidal air flow seems to vary in a wave form. The sudden increase of the velocity when it opens reaches the clown-stream, which seems to increase the quantity of the inspiration. The quantity of the inspiration on the atrial valve side seems to be always larger than that on the opposite side.
7. The trachea becomes gradually narrower as it goes further from the stigma, . In such a shape of the trachea, the velocity of inspiration seems to become gradually faster as it goes toward the down-stream by changing a part of the pressure of inspiration into the energy of motion. The trachea which is located near the stigma becomes gradually wider as it goes further from the stigma. In such a shape of the trachea, a part of the energy of motion of the inspiration seems to change into pressure with a high rate in the direction of the down-stream. The latter shape of the trachea is nothing but the former one when placed the other way around. Therefore, this shape seems to make the flow of the expiration easy, and hereupon the theory, that the carbonic acid gas is isolated into \V de trachea also, will be said to be affirmed.
8. Compared to all other trachea, in the sack-like trachea in the 8th abdominal segment:
(1) The shape of its transverse section is elliptical. The frictional drag of the flow in the elliptical tube can be considered smaller than when it is transformed into a circular tube. Therefore, the quantity of the fluid seems to increase that much.
(2) The dimension of its transverse section is larger than the longitudinal trachea (×1.39). Consequently the quantity of the fluid seems to increase that much.
(3) The angle of narrowing in some branches from the sack-like tracheae (approx.19°) is large compared to other tracheae (less than 8°) and tracheoles (less than 2°). This also seems to increase the quantity of the fluid, since it is said that, the larger the “Siborarekata”(angle of narrowing) is, the less the loss of energy of the flow is.