C 



From the moment the heart begins to pulsate till it 

 ceases to beat, the aeration of the blood is constant, 

 and the function of respiration invariable; carbonic 

 acid is given off in the process, but the chemical 

 change produced in the blood is unknown; nor is there 

 any reason to suppose the formation of any substance 

 similar to sugar. In th production of a plant from a 

 seed, some reservoir of nourishment is needed before 

 the root can supply sap; and this reservoir is the coty- 

 ledon in which it is stored up in an insoluble form, and 

 protected if necessary during the winter, and rendered 

 soluble by agents which are constantly present on the 

 surface. The change of starch into sugar, connected 

 with the absorption of oxygene, may be rather com- 

 pared to a process of fermentation than to that of re- 

 spiration; it is a change effected upon unorganized 

 matter, and can be artificially imitated; and in most of 

 the chemical changes that occur when vegetable com- 

 pounds are exposed to air, oxygene is absorbed, and 

 carbonic acid formed or evolved. 



It is evident, that in all cases of tillage the seeds 

 should be sown so as to be fully exposed to the influ- 

 ence of the air. And one cause of the unproductive- 

 ness of cold clayey adhesive soils is, that the seed is 

 , coated with matter impermeable to air. 



and trout, seek spots where there is a constant supply of fresh water, as near the 

 sources of streams as possible, and in the most rapid currents where all stagnation 

 is prevented, and where the water is saturated with air, to which it has Been ex- 

 posed during its deposition from clouds. It is the instinct leading these fish to 

 seek a supply of air for their eggs which carries them from seas, or ialtes into the 

 mountain country; which induces them to move against the -stream, and 

 our to overleap weirs, mill-dams, and cataracts, 



