Sect. II. i. i. DEFINITIONS. 



SECT. II. i. 



EXPLANATIONS AND DEFINITIONS, 



I. Outline of the animal economy. — II. I. Of the fenforium. (ft. 

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

 lar fibre. 5. The immediate organs of fenfe. 6. The external 

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

 9. Senfation. 10. Recolleclion and fuggefikn. 1 1. Habit, caufa* 

 tion, aj/ociation, catenation. 12. Reflex ideas. 13. Stimulus defined* 



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 mail premife a very fhort outline of the animal economy. 



u>.<j> nt-^ii. jiB.i > in 



I. — 1. The nervous fyftem has its origin from the brain, and 

 is diftributed to every part of the body. Thofe 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 thefe 

 nerves terminate in the immediate organs of fenfe and mufcular 

 fibres, and if a ligature be put on any part of their pafTage 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 inteftznal canal, the arteries/ veins, glands, and ab- 

 sorbent veftels. 



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

 probably confifh of moving fibrils, with a power of contraction 

 fimilar to that of the larger mufcles above defcribed. 



4. The cellular membrane confifts of ceils, which refemblc 

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

 necking 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 



