Cuvierian Si/stem qfZoologi/, 315 



boiling water. Albumen contains nearly all the elements 

 which can enter into the composition of each animal, as lime 

 and phosphorus, which harden the bones of vertebrated ani- 

 mals, the iron which colours the blood, the fat and animal oil 

 which are disposed in the cellular texture to soften it, &c. All 

 the liquids and solids of the animal body are composed of 

 chemical elements contained in the blood ; and it is only by 

 abstracting some of these elements, or by varying the propor- 

 tions, that they differ from each other ; in a few instances, an 

 addition is made of some other element. These operations, 

 by which the blood supports the solid parts of the body, are 

 called nutrition ; the production of the liquids is generally 

 called secretion. The blood which nourishes the body, is 

 continually changing its properties ; but it is restored by diges- 

 tion, which furnishes new matter ; and by respiration, which 

 discharges the superfluous carbon and hydrogen ; while trans- 

 piration, and various excretions, carry away other superabun- 

 dant principles. 



The perpetual transformations of chemical composition 

 constitute a condition of vital action, not less essential than the 

 circulation and the internal motions of the parts ; indeed, the 

 latter only serve to effect these transformations. 



The muscular fibre is the organ of animal motions, both of 

 those which follow the action of the will, and those which are 

 independent of volition, as the peristaltic motion of the intes- 

 tines, and the pulsation of the heart and arteries. The will 

 causes the muscular fibre to contract, by the intermediate 

 action of the nerves ; and, as all the muscular fibres which 

 produce involuntary motions are also accompanied by nerves, 

 it is therefore probable that it is the nerves which produce 

 muscular contraction in the latter. 



In order to account for the action of the nerves upon the 

 muscular fibres, Cuvier, with other physiologists, admits the 

 existence of a nervous fluid, which is not, however, like the 

 other fluids of the body, confined in tubes, vessels, or pores, 

 but is imponderable, like heat and electricity, though he sup- 

 poses it to be secreted by the medullary matter. According to 

 our author, the medullary matter of the brain and nerves is a 

 conductor of the nervous fluid ; all the other organic elements 

 are non-conductors, and arrest its progress, in the same man- 

 ner as glass is a non-conductor of electricity. 



Every contraction, and, in general, every change of dimen- 

 sion in nature, is effected (s^opere) by a change of chemical 

 composition : sometimes, this is nothing more than the afflux 

 or retreat of an imponderable fluid, such as caloric ; by this 

 the most violent motions known on the earth are produced, as 



