Gas pockets were formed by injection of air into the dorsal subcutaneous tissue of rats. While the morphological reactions of the subcutaneous tissues due to air injection have been described, little attention has been given to the relation between the structural changes of the tissue surrounding the pocket and the gas tensions inside the pocket. Gas tensions in the pockets were measurd varied days after formation of gas pockets. Histological sections were obtained from the pockets 10 and 30 days after initial air injection. The morphological changes in the tissue surrounding the pockets were observed.
The gas pockets have proved to be a useful means to estimate gas tensions in the tissue. When estimating O₂ tension in the subcutaneous tissue with the pocket, the possible O₂ tension difference between O₂ tension in the pocket and that in the tissue surrounding the pocket may be a matter of concern. By measuring gas tensions in the pockets and the overall O₂ consumption of rats breathing gas mixtures of varied O₂ tensions, it is possible to get information on the O₂ tension difference between the pocket and the blood perfusing the pocket-tissue.
Data of this experiment lead to the following conclusions:
(1) O₂ tensions in the pockets went down and CO₂ tensions tended to elevate as the days went by after preparation of the gas pockets.
(2) A granulomatous tissue layer proliferated on the inner surface of the pocket and this layer grew thicker as the days went by after initial air injection.
(3) When applying the subcutaneous gas pockets to the physiological study, it seemed reasonable to use the pockets only formed on the same day.
(4) The overall O₂ consumption of rats breathing pure O₂ under 1 ATA was 3.27ml. 100g B. W.^-1 min^-1. in average. There was no statistically significant difference between the O₂ consumption of rats breathing pure O₂ under 1 ATA and that breathing pure O₂ under 2 ATA.
(5) The difference between O₂ tension in the pocket and that in the blood perfusing the surrounding tissue of the pocket was greater under higher inspired O₂ tension than under lower inspired O₂ tension.

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A study was made of elimination of avrious inert gases from subcutaneous gas pockets in rats breathing room air under 1 ATA. Inert gases used in this present study was methne, ethane, nitrous oxide and xenon.
For interpretation of data, the elimination rate was defined which permitted the distinction of the most important physical properties of inert gases contributing to the elimination of inert gases from the pocket. The elimination rate of gas X was defined as the ratio of the volume of gas X eliminated from the pockets by a unit time to the volume of gas X in the pocket.
Further, the elimination rate of gas X devided by its solubility coefficient in the blood was defined as the corrected elimination rate of gas X. This enabled to discriminate the degree of the perfusion-dependancy of inert gases during elimination from the pockets.
A method was presented which enabled to estimate the amount of blood flow in the tissue surrounding the pocket without assuming that the elimination of inert gases is perfectly perfusion-dependent.
Based on data of this study, following conclusions were introduced:
(1) The solubility coefficient of gases in the blood was one of the most important factors contributing to the elimination of uses from the pockets.
(2) The degree of the perfusion-dependancy of inert gases during the elimination from the pockets seemed to be different from each gas. As to the grade of perfusion-dependancy of inert gases used in this study, nitrous oxide is the highest, followed by xenon, methane and ethane.
(3) By simultaneous measurement of the elimination rates of more than two inert gases from the pocket, it would be possible to estimate the amount of the blood flow in the pocket-tissue without assuming the perfect perfusion-dependancy of inert gases. Application of this method to the present experimental data, assuming the solubility and the diffusion coefficients of inert gases in the pocket-tissue were equal to those in water, led to the result that the blood flow in the pocket-tissue was 55.0ml. hr^-1.

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To estimate the diffusive conductance of carbon monoxide (CO) in the subcutaneous tissue quantitatively, the elimination of CO from rat's subcutaneous gas pockets was studied. The CO diffusive conductance in the tissue surrounding the pocket was defined as the ratio of the volume of CO eliminated from the pocket by a unit time to the CO tension difference between that in the pocket and the blood perfusing the pocket-tissue.
The CO diffusive conductance was measured under varied inspired O₂ tensions to deal with the relative significance of the CO diffusive conductance in the tissue layer between the blood in the capillary and the gas in the pocket as compared with the diffusive conductance of red cells to take up CO in the capillary. Inspired O₂ tension was ranged from 150mmHg to 1500mmHg.
It has been described that the amount of the blood flow has the effect upon the CO diffusive conductance. Therefore, when we compare the value of the CO diffusive conductance under one condition with that under another condition, it is necessary to take into account the change in the blood flow. To get informations on the blood flow in the pocket-tissue, the elimination of methane from the pocket was studied under varied inspired O₂ tensions.
Analysis of data in this study leads to the following conclusions:
(1) The CO concentration in the pocket showed a straight line relationship with time when plotted semilogarithmically. The exponential rate constant of the elimination of CO from the pockets of rats breathing room air under 1 ATA was 8.7×10^-3·min^-1.
(2) The CO diffusive conductance in the tissue surrounding the pockets of rats breathing room air under 1 ATA was 1.13×10^-4ml. mmHg^-1·min^-1.
(3) There was no statistically significant difference in the CO diffusive conductances and the amount of the blood flow perfusing the pocket-tissue when breathing gas mixtures of varied O₂ tensions.
(4) The CO diffusive conductance in the tissue layer between the pocket gas and the capillary blood seemed to be remarkably smaller than that of red cells to take up CO in the capillary.

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Pulmonary surfactant (phospholipid) is known to stabilize the pulmonary alveoli, but the exact relation between this material and mucopolysaccharide over the alveolar lining layer has not been established.
The purpose of this study was to clarify the histochemical characteristics of the alveolar lining layer on the submolecular level, with special reference to phospholipid and mucopolysaccharide. The pulmonary alveoli of the adult rabbits has been investigated electronhistochemically in normal state and experimental acute hypoxia induced by nitrogen gas inhalation.
(1) Phospholipid derivatives were demonstrated by means of Dermer's tricomplex flocculation method. The positive reactions were observed in the alveoalr lining layer and in the lamellar structure of the type II alveolar cells in either case. However, in the hypoxic group the staining intensity of the lining layer had a tendency to decrease.
(2) Mucopolysaccharide was demonstrated by both periodic acid methenamine silver (PAM) and modified-ruthenium red (RR) stains. The inclusion bodies of the type II alveolar cells was stained intensely by PAM and RR stainings. The lamellar and lattice structures occasionally were found within the alveolar spaces which were considered to represent free surfactant, also stained by RR staining. It was indicated that the inclusion bodies were probably related to the production of not only phospholipid, but also of mucopolysaccharide. Mucopolysaccharide layer demonstrated by RR had a tendency to increase in the hypoxic state, in contrast with the above described phospholipid layer was decreased. Furthermore, this layer was observed to be much thicker on the type II alveolar cells than the type I alveolar cells. It was speculated that such difference of the surface staining between the type I and the type II cells might be due to varied contents of sialomucin reported by Adamson et al. In addition, cellular sensitivity to hypoxia might be different in each cell type, based on the fundamental structural differences.
(3) An alveolar lining layer was not found to be consisted of two separate laminae which was reported by Kikkawa et al. and Weibel et al. The results obtained suggested that the alveolar lining layer was composed of a complex of phospholipid and mucopolysaccharide and might act as stabilizing agent of pulmonary alveoli.

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