SECT. XXXIX. 8. 7. GENERATION. 421 



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

 becaufe the fpecific attraction to the rubbed glafs or feaiing wax 

 can be withdrawn or rettored ; to which may be added, that 

 fome chemical combinations may arife from the (ingle 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 thole bodies, 

 which are held together by the fimple attraction probably of 

 one of them to the other ; which other pofTeffes 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 

 ftronglv 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 of the other. ThusI fulpect that carbon and oxygen rufli 

 together by their reciprocal attractions producing explofion, and 

 being afterwards not eafily feparable ; while azote or nitrogen is 

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

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

 cum (lance could be nicely afcertained, 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 phofphb- 

 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 conceptions of the adjunctions or 

 concretions obfervabie in organized or animated bodies ; which 

 conftitute their formation, their nutrition, and their growth. 

 Thefe may be divided into two kinds ; firft the junction or 

 union of animated bodies with inanimate matter, as when fruit 

 or flefh is fwallowed into the ftomach, and becomes abforbed 

 by the lacleals ; and the fecond, where living particles coalefce 

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

 junftion of the parts of living animals. 



In reipecl to the former the animal parts, as the noftrils and 

 palate, poffefs an appetency, when (limulated by the fcent and 

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

 inanimate material poflefles an aptitude to be thus united with 

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

 lowed 



