362 DIGESTION, SECT. XXXVII. 3. i. 



agreeable to its tafte from the blood, but every individual pore 

 acquires by animal fele^ion the material, which it wants ; and 

 thus nutrition feems to be performed in a manner fo fimilar to 

 fecretion ; that they only differ in the one retaining, and the 

 other parting again with the particles, which they have feleled 

 from the blood. 



They may, indeed, differ in another circum fiance ; that in 

 nutrition certain particles of the circulating blood, which have 

 not prevfoufly been ufed in the fyflem, are embraced, and form 

 a folid part of the animal. Whereas in fome of the fecretions, 

 thofe particles appear to be imbibed by the glands, which have 

 already been ufed in the fyftem, and probably abraded or de- 

 tached from it into the circulation : thefe are depoGted in refer- 

 voirs for future ufe, as bile and mucus ; or excluded for other 

 purpofes, as femen and tears ; or evacuated fimply as feces and 

 urine. And it fhould be obferved, that all the fecretions are 

 produced from their glands, in a very dilute date, mingled, I be- 

 lieve, with mucus diflblved in water : which is in part re-ab- 

 forbed from the refervoirs of the glands, or from the cells or 

 furfaces of the body, that no unneceflary wafte of animal mat- 

 ter may occur ; which accounts for the urinary bladders of fifh, 

 which would otherwife appear to be unneceflary, according to 

 the obfervation of Munro. 



This way of accounting for nutrition from ftimulus, and the 

 confequent animal fele&ion of particles, is much more analo- 

 gous to other phenomena of the animal microcofm, than by 

 having recourfe to the microfcopic animalcula, or organic par- 

 ticles of Buffbn and Needham ; which being already compound- 

 ed mud themfelves require nutritive particles to continue their 

 own exiftence. And muft be liable to undergo a change by our di- 

 geftive or fecretory organs; otherwife mankind would foon refem- 

 ble by their theory the animals which they feed upon. He, who 

 is nourifhed by beef or venifon, would in time become horned ; 

 and he, who feeds on pork or baeon, would gain a nofe proper 

 for rooting into the earth, as well as for the perception of odours. 



The whole animal fyftem may be conlidered as confiding of 

 the extremities of the nerves, or of having been produced from 

 them ; if we except perhaps the medullary part of the brain 

 refiding in the head and fpine, and in the trunks of the nerves. 

 Thefe extremities of the nerves are either of thofe of locomotion, 

 which are termed mufcular fibres ; or of thofe of fenfation, 

 which conftitute the immediate organs of fenfe, and which have 

 alfo their peculiar motions. Now as the fibres, which confti- 

 tute the bones and membranes, poflefled originally fenfation and 

 motion ; and are liable again to poflefs them, when they become 



inflamed ; 



