3^ DIGESTION, Sect. XXXVII. 3. r, 



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

 acquires by animal felection 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 fele&ed 

 from the blood. 



They may, indeed, differ in another circumftance •, that in 

 nutrition certain particles of the circulating blood, which have 

 not previouily been ufed in the fyftem, are embraced, and form 

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

 thofe particle3 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 depofited 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 mould be obferved, that all thefe fecretions are* 

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

 lieve, with mucus diffolved in water ; which is in part re-ab- 

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

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

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

 which would othervvife appear to be unneceffary, according to 

 the observation of Munro. 



This way of accounting for nutrition from ftimulus, and the 

 confequent animal felection 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 Buffon and Needham ; which being already compound- 

 ed muft themfelves require nutritive particles to continue their 

 own existence. And muft be liable to undergo a change by our di-> , 



'.live or fecreiory organs ; otherwife mankind would foon refer' 

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

 is nourished by beef cr venifon, would in time become horned ; 

 and he, who feeds on pork or bacon, would gnin a nofe proper 

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



The whole animal fyftem may be confidered as confiding of 

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

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

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

 The fe mities of the nerves are either of thofe of locomotion, 



are termed mufcular fibres ; or of thole of fenfation, 

 which cenftitute tl mediate organs of fenfe, and which have 



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

 tute the bones and membranes, poffefled originally fenfation and 

 motion ; and are again topollefs them, when they become 



inflamed ; 



