120 On muscular Motion. 



that a voluntary nniscle probably governs the operations of 

 the battery. 



The matter of the nerves and brain is very similar in alj 

 the diiferent classes of animals. 



The external configuration of animals is not more varied 

 than their internal structure. 



, The bulk of an animal, the limitation of its existence, 

 the medium in which it lives, and the habits it is des- 

 tined to pursue, are each, and all of them, so many indica- 

 tions of the complexity or simplicity of their internal struc- 

 ture. It is notorious that the number of brgans, and of 

 members, is varied in all the different classes of animals : 

 the vascular and nervous systems, the respiratory and di- 

 gestive organs, the parts for procreation, and the instru- 

 ments of motion, are severally varied, and adapted to the 

 condition of the species. This modification of anatomical 

 structure is extended in the lowest tribes of anin)als until 

 the body appears to be one homogeneous substance. The 

 cavity for receiving the food is indifferently the internal or 

 external surface ; for they may be inverted, and still con- 

 tinue to digest food : the limbs, or fentacula, may be cut 

 ofl", and they will be regenerated without apparent incon- 

 venience to the individual : the whole animal is equally 

 sensible, equally irritable, equally alive : its procreation is 

 genmiiferous. Every part is pervaded by the nutritious 

 juices, every part is acted upon by the respiratory influence, 

 every part is equally capable of motion, and of altering its 

 figure in all directions, whilst neither blood-vessels, nerves, 

 nor muscular fibres are discoverable by any of the modes of 

 investigation hitherto instituted. 



From this abstract animal (if such a term may be ad- 

 mitted) up to the human frame, the variety of accessory 

 parts, and of organs by which a complicated machinery is 

 operated, exhibit infinite marks of design, and of accom- 

 modations to the purposes which fix the order of nature. 



In the more complicated animals there are parts adapted 

 for trivial conveniences, much of their materials not being 

 alive, and the entire offices of some liable to be dispensed 

 with. The water transfused throughout the intersticial 

 spaces of the animal fabric ; the combinations with lime in 

 bones, shells, and teeth ; the horns, hoofs, spines, hairs, 

 feathers, and cuticular coverings, are all of them, or the 

 principal parts of their substance, extra-vascular, insensi- 

 ble, and unalterable bv the animal functions after they are 

 completed. I have formed an opinion, grounded on exten- 

 sive observation, that many more parts of animal bodies 



may 



