INTRODUCTION. I.") 



Tli8 functions of the animal body are divided into two classes : 



The animal functions, or those proper to animals, that is to say, sensi- 

 bility and voluntary motion. 



The vital, vegetative functions, or those common to animals and vege- 

 tables, i. e., nutrition and generation. 



Sensibility resides in the nervous system. 



The most general external sense is that of touch ; it is seated in the 

 skin, a membrane that envelopes the whole body, which is traversed in 

 every direction by nerves whose extreme filaments expand on the surface 

 into papillae, and are protected by the epidermis and other insensible tegu- 

 ments, such as hairs, scales, &c. &c. Taste and smell are merely delicate 

 states of the sense of touch, for which the skin of the mouth and nostrils 

 is particularly organized : the first, by means of papilla more convex and 

 spongy; the second, by its extreme delicacy and the multiplication of its 

 ever humid surface. We have already spoken of the ear and the eye. 

 The organ of generation is endowed with a sixth sense, seated in its in- 

 ternal skin ; that of the stomach and intestines declares the state of those 

 viscera by peculiar sensations. In fine, sensations more or less painful 

 may originate in every part of the body through accident or disease. 



Many animals have neither ears nor nostrils, several are without eyes, 

 and some are reduced to the single sense of touch, which is never absent. 



The action received by the external organs is continued by the nerves 

 to the central masses of the nervous system, which, in the higher animals, 

 consists of the brain and spinal marrow. The more elevated the nature of 

 the animal, the more voluminous is the brain and the more is the sensitive 

 power concentrated there ; the lower the animal, the more the medullary 

 masses are dispersed, and in the most imperfect genera, the entire nervous 

 - substance seems to melt into the general matter of the body. 



That part of the body which contains the brain and principal organs of 

 sense, is called the head. 



\VTien the animal has received a sensation, and this has occasioned vo- 

 lition, it is by the nerves, also, that this volition is transmitted to the 

 muscles. 



The muscles are bundles of fleshy fibres whose contractions produce all 

 the movements of the animal body. The extension of the limbs and every 

 elongation, as well as every flexion and abbreviation of parts, are the ef- 

 fects of muscular contraction. The muscles of every animal are arranged, 

 both as respects number and direction, according to the movements it has 

 to make ; and when these motions require force, the muscles are inserted 

 into hard parts, articulated one over another, and may be considered as so 

 many levers. These parts are called bones in the vertebrated animals, 

 where they are internal, and are formed of a gelatinous mass, penetrated 



