110 ANIMAL LIFE 



out from the mouth till it is wrong side out. Indeed, the 

 bodies sometimes burst. Their bodies are accustomed to 

 this great pressure, and when this outside pressure is sud- 

 denly removed the body may be bursted. Sometimes 

 such a fish is raised from its proper level by a struggle 

 with its prey, when both captor and victim may be de- 

 stroyed by the expansion of the body. Some fishes die on 

 being taken out of water through the swelling of the air 

 bladder and the bursting of its blood-vessels. If an animal 

 which lives normally on the surface of the earth is taken 

 up a very high mountain or is carried up in a balloon to a 

 great altitude where the pressure of the atmosphere is 

 much less than it is at the earth's surface, serious conse- 

 quences may ensue, and if too high an altitude is reached 

 death occurs. This death may be in part due to the diffi- 

 culty in breathing in sufficient oxygen to maintain life, but 

 it is probably chiefly due to disturbances caused by the 

 removal of the pressure to which the body is accustomed 

 and is structurally adapted to withstand. A famous bal- 

 loon ascension was made in Paris in 1875 by three men. 

 After the balloon had reached a height of nearly 24,000 

 feet (almost five miles) the men began to lose conscious- 

 ness. On the sinking of the balloon to about 20,000 feet 

 the men regained consciousness again and threw out bal- 

 last so that the balloon rose to a height of over 25,000 feet. 

 This time all three became wholly unconscious, and on the 

 balloon sinking again only one regained consciousness. 

 The other two died in the foolhardy experiment. All liv- 

 ing animals are accustomed to live under a certain pres- 

 sure, and there are evidently limits of maximum or mini- 

 mum pressure beyond which no animal at present existing 

 can go and remain alive. 



But in the case both of temperature and pressure con- 

 ditions it is easy to conceive that animals might exist which 

 could live under temperature and pressure conditions not 

 included between the minimum and maximum limits of each 



