194 Scientific Intelligence, — Zoology. 



gentle and continuous ; the organized portion remaining passive 

 and motionless ; this mode of respiration is seen in plants. In 

 the second, there is established an excessively rapid attraction 

 and repulsion between the organized parts and the surrounding 

 medium, whence a vibration results on the edge of the respira- 

 tory organs. Such is the respiration of a great number of the 

 Infusoria?, the Vorticella?, the Kalpodes, the Leucophylles, the 

 Rotiferse, &c. ; and amongst the animals of the radiata, the 

 Plumatelles, the Acalephes; among the Mollusca, the Planorbes, 

 the Lymneae, the Uniones, and the Anodontes. In the third mode 

 of respiration, the reciprocal action of the organized parts and 

 the surrounding medium goes on in determinate intervals, se- 

 parated by a moment of repose. Such is the respiration of the 

 higher animals.— 2. In birds, the air penetrates not solely into 

 the lungs, and about the parietes of the chest ; it also enters by 

 foramina not very determinate, into eight pneumatic pouches, 

 which occupy a large portion of pectoro-abdominal cavity. * 

 Thence it penetrates into subcutaneous cellules, by means of the 

 subscapular and subfemoral pneumatic pouches, and through 

 the apparatus already described into the superior and inferior 

 extremities. — 3. The pneumatic pouches are so placed, that they 

 can easily conduct the air into the more solid parts of the body, 

 and may in this way surround the heaviest viscera, so that it 

 supports birds during their flight, and thus contributes to faci- 

 litate their aerial locomotion. — 4 The large' quantity of air 

 which thus finds its way into the most internal parts of their bo- 

 dies, tends to dry the marrow in the interior of the bony cavi- 

 ties, and also a portion of the fluids which it encounters in its 

 passage ; hence results a diminution of the specific gravity of 

 birds, the true cause of which has in vain been sought for in the 

 quantity of air alone which penetrates into their bodies. — 5. In 

 birds, the oxidation of the nutritive juices is effected not only in 

 the lungs, but is much promoted also in the pneumatic pouches. 

 The air contained in them operates, through the membranes, 

 upon the sanguiferous and lymphatic vessels with which they 

 are in contact ; hence there follows a far more complete and 

 speedy oxidation. — 6. Not the skeleton only, but all the viscera 

 also, which go to form the body of birds, are much more per- 

 The air-cells of English anatomists. 



