374 RESPIRATION. 



than we usually meet with in bronchial or pulmonary respiration. 

 The oxygen which is absorbed by the intestine passes, therefore, 

 into the mass of the blood, and the carbonic acid to which it 

 gives rise is not eliminated by the intestine, but through the 

 gills; hence we also find, from Baumert's experiments, that in the 

 bronchial respiration of these animals there is a far greater 

 exhalation of carbonic acid in proportion to the inspired oxygen, 

 than in the previously-named fishes. Special observations further 

 showed that the pond-loach very seldom employs the intestinal 

 respiration in fresh water, which contains a richer supply of 

 oxygen, although in water which is poor in this gas, it very 

 frequently cornes to the surface in order to swallow air; yet these 

 animals do not appear capable of supporting life by only one of 

 these functions ; they sicken when respiring through the gills only, 

 almost as quickly as when they are limited to intestinal respiration. 

 The experiments which were made upon pond-loaches by the 

 same method employed with the tench and gold-fish yielded the 

 following results : 1000 grammes of pond-loaches inspired on an 

 average 0*031 6 of a gramme of oxygen, and exhaled 0*0543 of a 

 gramme of carbonic acid in the hour ; these animals, therefore, 

 gave off more oxygen in the form of carbonic acid than they had 

 absorbed through the gills ; since for 100 parts of oxygen absorbed 

 through the gills, 124*9 grammes were eliminated with the 

 carbonic acid. This result fully agrees with the comparative 

 analyses made by Baumert of the air which was swallowed, and 

 that which was again excreted through the intestine ; for whilst the 

 air in the intestine showed a diminution of the oxygen amounting 

 to 8 or 11 by volume, the carbonic acid had only increased about 

 2g- at most. Baumert's analyses have further shown the probability 

 that pond -loaches always absorb a certain quantity of nitrogen 

 during respiration. 



Of those animals which possess no special organs of respiration, 

 but accomplish their necessary interchange of gases by the skin 

 only, the earthworm is the only one which has been made the 

 subject of experimental investigation, and the only experiments of 

 the kind, which we possess, were made by Regnault and Reiset. 

 They prove that the respiration of these animals is very similar to 

 that of frogs, which also respire vigorously through the skin. The 

 consumption of oxygen, and the ratio of the oxygen contained in 

 the carbonic acid, are nearly the same as in the latter animals : 

 1000 grammes' weight of worms absorbed in one hour 0*1013 of 

 a gramme of oxygen, and exhaled 0-0982 of a gramme of carbonic 



