Sf.ct. XXXIX. 8. 7. GENERATION. 42 r 



fpecific aptitude to unite with the rubbed glafs or fealing wax ; 

 becaufe the lpecific attraction to the rubbed glafs or fealing wax 

 can be withdrawn or reftored ; to which may be added, that 

 fome chemical combinations may arife from the fingle attrac- 

 tion of one body, and the aptitude to be attracted of another. 

 Or they may be owing to reciprocal attractions of the two 

 bodies, as in what is termed by the chemifts double affinity, 

 which is known to be fo powerful as to feparate thofe bodies, 

 which are held together by the fimple attraction- probably of 

 one of them to the other ; which other pofYeiTes only an apti- 

 tude to be attracted by the former. 



It is probable, that in fome of the mod fimple combinations 

 of the particles of inanimate matter, two of them may be 

 ftrongly united by reciprocal attractions to each other ; that in 

 other fimple combinations two particles may be held together, 

 though lefs firmly, by the attraction of one and the aptitude to be 

 attracted o,f the other. Thus I fufpect that carbon and oxygen rufli 

 together by their reciprocal attractions producing explofion, and 

 being afterwards not eafily feparable ; while azote or nitrogen is 

 lefs firmly united with oxygen by the attraction of one of them, 

 and only the aptitude to be attracted of the other. If this cir- 

 cumftance could be nicely ascertained, the theory of chemical 

 affinities might poffibly advance a ftep further in the explana- 

 tion of fome difficult phenomena, as of the heat generated in 

 the explofion of various materials, with which oxygen is more 

 loofely united, when applied to ignited carbon ; as of the acid 

 of nitre, and feveral metallic oxydes ; as well as of the general 

 circumftances of combuftion and inflammation, as of phofpho- 

 rus in the atmofphere, and of oil of cloves with nitrous acid. 



7. The above account of the tendencies to union of unor- 

 ganized or inanimate matter is not given as a philofophical 

 analogy, but to facilitate our conception of the adjunctions or 

 concretions obfervable in organized or animated bodies ; which 

 conftitute their formation, their nutrition, and their growth. 

 Thefe may be divided into two kinds ;.fir(l the junction or 

 union of animated bodies with inanimate matter, as when fruit 

 or nefh is fwallowed into the ftomach, and becomes abforbed 

 by the lacteals; and the fecond, where living particles coalefce or 

 concrete together ; as in the formation, nutrition, or conjunc- 

 tion of the parts of living animals. 



In refpect to the former the animal parts, as the noflrils and 

 palate, poflefs an appetency, when ftimulated by the icent and 

 flavour of agreeable food, to unite themfelves with it ; and the 

 inanimate material pofiefles an aptitude to be thus united with 

 the animal organ. The fame occurs, when the food is fwal- 



lowed 



