ASSIMILATION. 651 



MM. Becquerel and Breschet have found that when a dog or 

 rabbit is deprived of its hair, and the whole body covered with a 

 varnish to prevent perspiration, the animal always died in a few 

 hours, while the temperature of the surface rapidly sank. In a 

 rabbit from 101 to 76 in an hour. . In another the temperature 

 of the muscles of the thigh in an hour and a-half was only 5^ 

 above that of the atmosphere.* 



CHAPTER V. 



OF ASSIMILATION. 



WE have now seen the progress of digestion, and the forma- 

 tion of blood, as far at least as we are acquainted with it. But 

 to what purposes is this blood employed, which is formed with so 

 much care, and for the formation of which so great an appara- 

 tus has been provided ? It answers two purposes. The parts of 

 which the body is composed, bones, muscles, ligaments, mem- 

 branes, &c. are continually changing. Jn youth they are increas- 

 ing in size and strength, and in mature age they are continually 

 acting, and consequently continually liable to waste and decay. 

 They are often exposed to accidents, which render them unfit for 

 performing their various functions ; and even when no such acci- 

 dent happens, it seems necessary for the health of the system that 

 they should be now and then renewed. Materials, therefore, must 

 be provided for repairing, increasing, or renewing all the various 

 organs of the body ; phosphate of lime and gelatin for the bones, 

 fibrin for the muscles, albumen for the cartilages and membranes, 

 &c. Accordingly, all these substances are laid up in the blood ; 

 and they are drawn from that fluid, as from a storehouse, when- 

 ever they are required. The process by which the different in- 

 gredients of the blood are made part of the various organs of the 

 body 'is called ASSIMILATION. 



Over the nature of assimilation the thickest darkness still 

 hangs : there is no key to explain it, nothing to lead us to the 

 knowledge of the instruments employed. Facts, however, have 

 been accumulated in sufficient numbers to put the existence of 

 the process beyond the reach of doubt. The healing, indeed, of 



* Comptes Rend us, xiii. 791. 



