34^ Experiments and OhfervnttonS' 



It appears to me then that light deflroys the vital prin- 

 ciple of germs, and that after its dedniftion new combina- 

 tions arc formed. 



The colour, indeed, which the eggs ailumed during my 

 experiments, never manifelted iifelf without the deflrudion of 

 life, and it never iliowed Itfelf till the light had exercifed on 

 them a prettv ftrong aAion. 



The toial exhaudion of vitalilv elTctSlcd by light, ought 

 not to be different from iliat efie6led by other ftimuli ; that 

 js to fay, light weakens tlic germ, and confequently retard* 

 its cxpanfion: in a word, by weakening and exhaufting it 

 it cxtinguiilies its life; which is perfedlly agreeable ^o what 

 we have obfcrvcd in eggs retarded in the procefs of hatch- 

 ing, or which periflicd, according to the inteniity of the 

 light they had received. 



It might be conje6lured that the light affefts chiefly the 

 nervous fubllance of the tender embryos, becaufe we know 

 the vehemence with which it affe6ls, and in a very fcvere 

 manner, our retina, when its action on it is too long conti- 

 nued. The exidcnce of the pupillary membrane in the 

 fcetus, and ihe pain experienced by young animals when firil 

 expofed to the light, are further proofs in , favour of this 

 hypothecs. In my eggs I could difcover op the head of the 

 iufe6l thofe ,two hemifpheres, with facets which afterwards 

 formed the eyes of the infe6l-; ;a proof of their advanced or- 

 ganization. 



However plaufible this reafoning might be, I was defirous 

 of pulting it to the teft Ojf experiment. As vegetables have, 

 no nervous fubllance deftined for feeling, they appeared to 

 me proper for this purpofc^ t therefore took French beans, 

 (pba/cojus "julgar'is //i/Z7A.j) .chick pea s_, [cicer ariciinum) lu- 

 pines, {luplnus albus) and moiflened ijiem till they began to. 

 fliow i]gns of gernii nation. L then removed, the bark, and 

 put tiicn» thus peeled into, glafs tub<^s with a little watej:, 

 J imuicrrcd thefe tubes in a bottle of very thin tranfparent 

 gUfs filled with water; fome of the tubes I ha4 wrapped up 

 in a plate of lead, to flielter them from the light of the fun^. 

 and they were all kept at the fame temperature. I firfl ob- 



fervcd 



