IN LIVING AND DEAD MATTER. 677 



the proximate constituents of blood with the dif- 

 ferent organs, and in maintaining their healthy 

 activity, is carried off and removed from the sys- 

 tem,* with a rapidity corresponding with the 

 energy of the brain, muscles, stomach, &c. until 

 the vital affinities by which the molecules of ar- 

 terial blood are transferred to, and kept in a state 

 of combination with, the solids, is gradually di- 

 minished, and finally dissolved when, having 

 performed the office of renewing the structure 

 and vitality of the different tissues, they succes- 

 sively fall from their places, and are taken up 

 by the lymphatic absorbents, which convey them 

 into the general circulation as worn-out materials, 



* The caloric conveyed to the different glands in combination 

 with arterial blood, and in elaborating the various secretions, is 

 also expended by their action, when it passes out of the body 

 with the exhalations from the skin, lungs, and kidneys, or from 

 the surface by radiation. Were it not for this rapid expenditure 

 of blood and vital heat, the temperature of birds would be far 

 higher than it is, and their blood proportionally richer in organic 

 particles ; for we have seen that they consume at least double 

 the ratio of oxygen and of aliment as the same weight of mam- 

 malia. But as the functions of circulation, secretion, nutrition, 

 and muscular motion are more energetic in birds, their blood and 

 animal heat are transferred to the solids, and expended in main- 

 taining the renewal of their composition and vital force with such 

 rapidity, that their mean temperature, and the ratio of organic 

 particles in their blood, are not much higher than in mammalia. 

 For the same reason, the temperature of a man with large thorax 

 and sound lungs, does not much exceed that of one with a narrow 

 chest, diseased lungs, and imperfect respiration, because in the 

 former, it is more rapidly expended by secretion, nutrition, sensa- 

 tion, and locomotion. 



