FISHES. 373 



gill-breathing animals since Humboldt and Provenal prosecuted 

 their experiments on the respiration of fishes. We find from 

 these observations, which were most admirable for the time at 

 which they were undertaken, that also in this form of respiration 

 the oxygen which is absorbed exceeds that which is exhaled in the 

 form of carbonic acid, the latter amounting in these experiments 

 to scarcely four-fifths of the absorbed oxygen, and frequently to 

 only half the quantity. Tiiese experiments yield, however, this 

 remarkable result, that fishes constantly absorb very large 

 quantities of nitrogen: and they show that fishes, like other 

 animals, transpire copiously through the skin. These animals, 

 moreover, are capable of breathing in atmospheric air as long as 

 their gills are moist, the products of respiration presenting under 

 these circumstances the same relations to the absorbed oxygen as 

 in water, which is an obvious proof that respiration in water- 

 breathing animals follows the same laws as those which control 

 atmospheric respiration. Baumert* has recently, by the aid of an 

 ingenious apparatus, made several interesting experiments on the 

 respiration of the tench (cyprinus tinea), the gold-fish (cyprinus 

 aureus), and the pond-loach (cobitis fossilis). It was shown by 

 these experiments, in the first place, that 1000 grammes' weight 

 of tench inspired on an average 0*0143 of a gramme of oxygen 

 in one hour, and exhaled 0*0138 of a gramme of carbonic acid ; 

 while, on the other hand, the same weight of the more lively gold- 

 fish absorbed 0*0409 of a gramme of oxygen, and eliminated 0*0419 

 of a gramme of carbonic acid in the same period of time. The 

 ratio of the volume of absorbed oxygen to that of exhaled carbonic 

 acid was very nearly as 10 : 7 ; for every 100 grammes of absorbed 

 oxygen 72*3 grammes are again expired with the carbonic acid. 

 In reference to the nitrogen, Baumert found sometimes a slight 

 absorption, and sometimes a slight exhalation. In experiments with 

 the pond-loach, results were obtained differing in several respects 

 from those which we have been describing; thus, for instance, 

 this fish, like some others, exhibits a special intestinal respiration, 

 for it absorbs air through the mouth as well as by the gills, swal- 

 lowing it on the surface of the water, and thus conveying it to the 

 stomach. Baumert analysed the air which was again eliminated 

 through the intestinal canal, and found that it contained much 

 less oxygen than the air which the fish had swallowed; the 

 oxygen had, however, been replaced by much less carbonic acid 



* Chem. Untersuch. iiber d. Kespiration des Sclilammpeizgers. Heidelberg, 

 1852. 



