SECT. II. i. i. DEFINITIONS. 3 



SECT. II. i. 



EXPLANATIONS AND DEFINITIONS. 



I. Outline of the animal economy. II. i. Of the fenforium. 2. 

 Of the brain and nervous medulla. 3. A nerve. 4. A mufcu- 

 lar fibre. 5. The immediate organs offenfe. 6. The external 

 organs of fenfe. 7. An idea or fenfual motion. 8. Perception. 

 9. Senfation. 10. Recolleflion andfuggejlion II. Habit > cauja*- 

 tion, ajficiation, catenation. \ 2. Reflex ideas. 1 3 . Stimulus dejined. 



As fome explanations and definitions will be neceflary in the profecu- 

 tion of" the work, the reader is troubled with them in this place, and 

 is intreated to keep them in his mind as he proceeds, and to take 

 them for granted, till an apt opportunity occurs to evince their truth ; 

 to which 1 ihall premifeavery ihort outline of the animal economy. 



I. i. THE nervous fyftem has its origin from the brain, and 

 is diftributed to every part of the body. Thofc nerves, which 

 ferve the fenfes, principally arife from that part of the brain, 

 which is lodged in the head ; and thofe, which ferve the pur- 

 pofes of mufcular motion, principally arife from that part of the 

 brain, which is lodged in the neck and back, and which is erro- 

 neoufly called the fpinal marrow. The ultimate fibrils of thefc 

 nerves terminate in the immediate organs of fenfe and mufcular 

 fibres, and if a ligature be put on any part of their pillage from 

 the head or fpine, all motion and perception ceafe in the parts 

 beneath the ligature. 



2. The longitudinal mufcular fibres compofe the locomotive 

 mufcles, whofe contractions move the bones of the limbs and 

 trunk, to which their extremities are attached. The annular or 

 fpiral mufcular fibres compofe the vafcular mufcles, which con- 

 ftitute the inteftinal canal, the arteries, veins, glands, and ab- 

 forbent veflels. 



3. The immediate organs offenfe, as the retina of the eye, 

 probably confift of moving fibrils, with a power of contraction 

 fimilar to that of the larger mufcles above defcribed. 



4. The cellular membrane confifts of cells, which refemble 

 thofe of a fponge, communicating with each other, and con- 

 necting together all the other parts of the body. 



5. The arterial fyftem confifts of the aorta and the pulmona- 

 ry artery, which are attended through their whole courfe with 



their 



