SECRETION AND ABSORPTION OF GAS, ETC. 129 



of Geneva, Hiifner found that the gas consisted sometimes 

 of perfectly pure nitrogen, 1 which must have had a tension 

 of six or seven atmospheres. Schloesing and Richard found 

 that the "nitrogen" from the air-bladder of Synapho- 

 branchus pinnatus contains about 1 "94 per cent, of argon. 

 The argon tension in the air-bladder at the depth at which 

 the animal was caught must thus apparently have amounted 

 to 35 per cent, of an atmosphere. Since the argon tension 

 of sea-water is presumably only "93 per cent, ot an atmo- 

 sphere it would thus seem as if even argon may be secreted 

 by the swimming-bladder. 



Moreau noticed that section of the sympathetic nerve 

 fibres going to the walls of the air-bladder seems to hasten 

 the secretion of gas into the empty bladder, and more 

 recently Bohr 2 has found that section of the vagus branch 

 entirely stops it. Thus the secretion of gas, like secretion 

 from the salivary or other glands, is under the control of 

 the nervous system. 



It has been known for lono that in the walls of the air- 



o 



bladder of many fishes there are present " retia miralulia," 

 i.e., bunches or discs o r finely divided vessels. These 

 structures are, however, beneath the lining epithelium, and 

 it is difficult to see how they can have any very direct con- 

 nection with the secretion of gas. The epithelium, however, 

 is often differentiated into a more or less gland-like structure 

 (the "epithelial body") which was described a few years 

 ago by Coggi. Anything like full and complete investiga- 

 tions of these structures do not seem to have been made yet, 

 although presumably the structures described by Coggi are 

 real air glands. 



As regards the process by which gas is secreted it is 

 difficult to avoid the conclusion that the molecules of gas 

 are liberated from some form of combination within the 

 cells lining the air-bladder. It seems not unlikely that this 

 process is continually going on, even while the actual 

 amount of gas in'the- bladder is not increasing. Moreau 



1 Archiv filr Anatomie u. ■Physio/ogie , 1892, p. 54. The argon was, of 

 course, not determined. 



2 Journ. of Phsiol., vol. xv., p. 494. 



9 



