123 



fluid, produce all the phenomena of sight. The eni'm&i 

 spirits are this fluid, which the brain extracts and pre- 

 pares, and continually conveys into the nerves, and by 

 the nerves into all parts, which it nourishes, moves, and 

 animates. 



2. An animal had in vain received senses, by means 

 of which it can distinguish between what is useful or 

 hurtful, if it were not able to give itself any motion for 

 the attaining the one, and avoiding the other. It is 

 therefore furnished with organs that procure to it. this 

 faculty. These organs are the muscles y which by the di- 

 latation and contraction, and by the lengthening and 

 shortening of the iibres that compose them, communi- 

 cate to all parts the motions, which are suited to the 

 wants of the animal. 



It is evident from experiments, that the nerves contri- 

 bute to the exercise of the muscles. The spirits which 

 they disperse therein, insinuate themselves into all the 

 vesicles, dilate them, and by that means put the organ 

 into action. 



One property of the muscular fibre (whose effects ar 

 diversified a thousand ways, the cause of which is con- 

 cealed from us) is that, by virtue whereof it contracts it- 

 self on the touch of any body either solid or liquid* 

 This is called irratabifity. By means of this, different 

 parts of the animal continue to move, after they have 

 been separated from the entire body ; and the heart 

 when detached from the breast, performs a number of 

 pulsations, which cease as soon as the blood in the cavity 

 is evacuated. 



3. From that part which gives admittance to the food 

 to that from whence issue the remains of the grosser 

 aliment, there is one continued canal, which is fonned, 

 differently in different parts of its extent. There are 

 three principal parts distinguished in it, the tesopkagus, 

 the stomach, and the intestines. All these are formed 

 of various membranes laid on each other, and which 

 are themselves composed of fibres differently interwo- 

 ven. The muscles, wherewith one or several of these 



vol.. iv. G 



