GENERATION. 



flituted for tliofe of tlie female plant. The fame circum- 

 ftances will occur in the human fpecies if the offspring of 

 an European woman by a negro be fecundated by a negro ; 

 and the produce of that conception again by a negro, &c. 

 Thus, at l.-<!l, the preformation of the maternal germ, which 

 has been preferved fince the creation of the world, avails 

 nothing, but yields entirely to the formative power of the 

 male fluid, wiiich, according to the hypothefis of evolution, 

 fhould merely excite it to aftion. We may affirm, in fliort, 

 on the whole, that of all the phenomena adduced in fupport 

 of this hypothefis, not one can be eflablidied fufficiently 

 clear to be admitted as a proof ; while there arc numerous 

 unexceptionable obfervations dir-'ctly oppoling it. 



But, in proportion as this hypothclia of evolution is in- 

 eonfiilcnt with the phenomena, and with the rules of philo- 

 fophifmg, fo, on the contrary, the opinion, not that any fic- 

 titious germs are evolved by means of conception, but that 

 the new being is in fact generated, and graduuliy and fuc- 

 eeflively formed from the generative fluids, commends itfelf 

 to our approbatio?) by its fimplicity, and its accordance with 

 the other procefles of nature. 



Since this affair of a tru'^ generation by f jccrlfive fonna- 

 tion has been varioufly explained by phyfiologills, I con- 

 ceive that we (hall approach mofl nearly to the truth, by 

 adopting tlie following propofitions. ill. The materials, 

 of which organizL-d bodies, and confequently the human 

 frame iscorapofed, differ from all other matter in being re- 

 gulated fimply and exclulively by vital powers. 2d. Of 

 thefe the moft remarkable, and that, whofe exiftence and 

 agency can be the leaft quellioned, is the force which afls 

 on organized matter, when prepared for its deflination, but 

 not yet moulded into fhape, and bellows on it, according 

 to its various natures, various but determined and definite 

 forms. In order to dillinguilh this vital power properly from 

 all others, I give it the name of nifus formativus. 3d. This 

 nifus formativus is imparted to the materials of genera- 

 tion, when they are contained in a mature ftate, under the 

 requifite conditions, in the uterine cavity, builds up in it the 

 rudiments of the embryo, and gradually forms its organs 

 to correfpond to their pre-ordained purpofes : it preferves 

 the fame ftrufture by the procefs of nutrition, as long as 

 life continues ; and it obviates the effefts of ca'fual mutila- 

 tion, as far as that can be aCcomplifhed, by means of re- 

 produftion, 



This gradual formation of new organized bodies can be 

 mofl manifeftly difccrned in thofe, which combine, with a 

 cohfiderable magnitude, a rapid growth, and fuch a kind 

 of delicate femi-tranfparent textvu-e, that they can be 

 clearly feen through, particularly in a fufficicnt light, and 

 with nioderate magnifying powers. This is the cafe in 

 the vegetable kingdom, witli fome flmple aquatic produc- 

 tions, as- the conferva fontinalis, which is propagated in the 

 early part of fpring ; in the bloodlefs divillons of the ani- 

 mal kingdom, with the polypes (hydra) ; in the animal king- 

 dom, with the incubated egg, on the firfl appearance of the 

 chicken, and its fubfequent daily developement. 



Itmuil be obfervcd here, that the exprtflion nifus foi-ma- 

 tivus is employed fimply for t!ie purpofe of diftingulfliing 

 this from the other kinds of vital powers, and by no means 

 witli any intention of explaining the caufe of generation. 

 1 believe the latter to be concealed by no lefs impenetrable 

 darknefs than that v.'hich involves the caufes of gravitation 

 and attraftion, which are only names for effefts, recognized 

 like the nifus formativus, a pofleriori. I have employed the 

 word nifus chieiiy in order to denote that the nature of this 

 force is truly vital, and to dillinguifh it as clearly as poffible 

 from the merely mcclvanical powers, by means of v.^hich 



fome philofophers formerly endeavoured to explain the bit- 

 iinefs of generation. The very point on which the whole 

 of this doftrine concerning the nifus formativus hino-cs, 

 and which alone fufficiently. diflinguifhes it from the vis 

 plaflica of the ancients, the vis effentialis of Wolf, and 

 other hypothefes of the like nature, confifls in the combina- 

 tion of the two principles, by which the nature of organ- 

 ized bodies is explained, viz. the phyfico-mechanical and 

 the teleological. 



I hold it moll probable, that in the firft place, a definite 

 time is required for the various fluids of each fex, which 

 feem to be united in the cavity of the uterus after a fruit- 

 ful copulation, to be more intimately mingled, and brought 

 to maturity. When the period of this preparation is com- 

 pleted, the mature and intimately blended fluids become 

 animated by the nifus formativus, by which the hitherto 

 unformed materials of generation are partly moulded into 

 the elegant coverings of the ovum, partly into the figure 

 of the contained embryo. Hence we can underfland, why 

 the fmalleit veilige of a formed fcctus cannot be difccrned, 

 even with the affillance of the excellent modern diop- 

 trical inflruments, during the tiril week after conception, 

 excepting the unformed fluids contained in the uterine 

 cavity ; while the embryo appears as it were on a fuddeii in 

 the third week. 



I fhould exceed the limits of thefe inflitutions, if I were 

 to recount at greater length thofe arguments drawn fro'tn 

 nature herfelf, by which the influence of the nifus format 

 tivus in generatioil feems to me to be rendered very highly- 

 probable. I fliall advert very fhortly to a few of thefe points, 

 the force of which will be cafily difcovered by a more at- 

 tentive conlideration. On. this principle I explain the me» 

 morable experiment in the hillor\' of hybrid productions,, 

 wliere prolific hybrids, fecundated during feveral genera- 

 tions, by the male feed of the fame fpecies, have produced 

 an oflspring gradually deviating from the original ma- 

 ternal form, and affuming the charaftcrs of the father,, 

 until at laft the former has been completely clianged into 

 the latter by a kind of arbitrary metamorphofis.. 



The well-known faft of the great frequency of mon- 

 flrous produftions in fome fpecies of doniillicated animals, 

 particularly fwine, and their rarity in the wild condition of 

 the fame animals, can only be explained on the principles 

 already flated. The evolutionifls are compelled to aflert 

 that all thefe monflroflties mufl have exifled in the germs 

 from the firfl creation of things. The phenomena of re-proi 

 duftion, taken altogether, can be much more aptly explain- 

 ed by the agency of the nifus formativus, than on the notion 

 of pre-exiflent germs ; and fome particular examples, as,, 

 for ini1ar.ce, of nails growing on the rniddlc, after the lofs 

 of the firfl phalanx, cannot well be folved on any otheC 

 principle. 



After confidcring, and carefully weighing the arguments' 

 on both fides of the quelHon, it appears, that even thofe 

 who affuine pre-exiflent germs, muft allow to the male femi- 

 nal fluid a confiderable formative influence, in addition to- 

 the exciting power, which they recogni-/e in it, and con- 

 fequently that the doftrine which they defend requires, in 

 faCt, the aflillance of the nifus formativus ; while the lat- 

 ter fufhciently explains the phenomena of generation, with- 

 out the aid of prc-exifting germs." Whatever theory of ge- 

 neration v.--e adopt, we muil ultiinateiy alcer.d to the agency 

 of the Creator, the primary caufe of all exiflence.. 



The circumflances belonging to the flate of pregnancy ; 

 the period and phenomena of parturition and its confequences,. 

 are treated under thofe articles of the Cyclopa;dia which 

 relate to the fubjetl of midwifery. 



Gene- 



