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germs. Two fetus's that are united only by the spin?, 

 perfectly resemble two fruits that are grafted ly con- 

 tact. An egg sometimes contains two solks, conse- 

 quently it then contains two germs. How easy a matter 

 is it for tiiem to engraft themselves together as- they 

 unfold ! We have seen a chicken with four feet, which 

 undoubtedly proceeded from a like union. The germs, 

 which are first fiuid, and for a considerable time gela- 

 tinous, are very penetrable. If they come in contact 

 they will mix together in part. Similar organ?, which 

 at least half penetrate each other, will subsist in tlie 

 other moiety. We see clearly this reciprocal penetra- 

 tion in a human fetus having two heads on a single 

 body. This monster was evidently formed of two moie* 

 ties of the fetus connected together. 



If their gelatinous state renders germs very penetrable, 

 it favours with much greater reasoii their union by .graft- 

 ing, or that of some parts to each other, either of the 

 same germ, or two or more germs. The graft is united 

 to- its subject only by gelatinous, or at least by herba- 

 ceous fibres : such fibres are proper for forming new 

 productions, and for connecting and intermingling to- 

 gether. Two polypus's unite together much more 

 easily than two rinds : they are abundantly softer. 



Ifj-. Accidental grafts may give birth to monsters, 

 which we should term inexplicable, by this principle ; 

 but you have not forgot that all organical parts have 

 forms and situations in the germ which differ prodigi- 

 ously from those they will Lave in the unfolded fetus, 

 Recall to mind the e/iick in its first form, its heait 

 in that of a simi-circie, and you will comprehend that 

 those conjunctions, which appear impossible to you in 

 the fetus, may be easily effected in the germ. 



The analogy of parts likewise favors their union: 

 this analogy results from that of the elements. Two 

 membranes are more- disposed to unite than a mem- 

 brane and a bone, and similar parts of the same organ 

 than, parts of different orgaua. 



