On the Swim-bladder Gases.

The formation of the swim-bladder gases of some sea and fresh water fishes were investigated and the results may be summarized as follows : 1. As a rule, oxygen content in the swim-bladder is higher in a fish living at greater depth than at shallow, and sea water fishes, than fresh water ones. 2. Oxygen content in the swim-bladder of the fish living at great depth decreases after 1-2 days stay in the aquarium. 3. Carbon dioxide content in the swim-bladder of all fishes examined is very small. 4. Through the poisoning of carbon monoxide, the swim-bladder gas decreases in its oxygen content and increases slightly in its carbon dioxide. 5. Corresponding to the artificial increase or decrease of the external pressures influencing the body surface of the fish, oxygen content of the swim-bladder gases increases or decreases respectively. 6. After the evacuation of the swim-bladder gases, newly formed gases always contain high oxygen percentage. 7. When oxygen or carbon dioxide of high concentration are injected in the swim-bladder, these gases diffuse out easily through the wall of the swim-bladder during 1-2 days. 8. Oxygen dissociation curve of carp blood is remarkably steep compared with the human blood, and influenced very much with the presence of carbon dioxide so as to decrease the affinity of the blood to oxygen. 9. Histological examination of the swim-bladder of Sebastiscus marmoratus and Carassius auratus indicate characteristic structure of the blood capillaries which distributed in the internal layer of membranes and sinus-like dilated. 10. From the above experimental results, some considerations on the gas formation in the swim-bladder were offered.