THEORY OF SECRETION AND NUTRITION. (J69 



mosphere by respiration, and wholly arrested or 

 greatly diminished whenever the temperature of 

 the body is reduced much below the normal 

 standard by immersion in cold water, or during 

 the cold stage of fever, cholera, &c. 5. That if 

 the temperature of blood be not raised above that 

 of the solids, it cannot excite the stomach to se- 

 crete gastric juice, nor any of the other glands 

 their respective fluids. 



Again; that neither secretion nor nutrition 

 depend on nervous influence, is evident from the 

 fact, that the germs of all animals are generated 

 by secretion, and developed by nutrition, before 

 any part of the nervous system is formed, as 

 stated in the preceding chapter, p. 592. Yet we 

 are informed by Dr. Roget, in an article on 

 Animal Physiology, contained in the Library 

 of Useful Knowledge, p. 92, that " the nervous 

 system exerts a certain action upon the blood, 

 by which are maintained the secreting and other 

 assimilating processes, a disengagement of caloric 

 produced, and the temperature necessary to ani- 

 mal health sustained." He also adds in his late 

 elaborate Bridgewater Treatise, that " not only 

 muscular contraction, but the organic affinities 

 which produce secretion, and all those unknown 

 causes which effect nutrition, development, and 

 growth of each part, are placed under the control 

 of the nervous power." (Vol. ii. p. 357.) 



Similar views have been offered by Tiedemann, 



