GENERATION. 



429 



Burdach that the generative function, com- 

 prising the production of a fruitful egg and the 

 formation of the young animal from it, are 

 natural phenomena not more secret in their 

 essence than others occurring in organized 

 bodies, and which, therefore, ought to be 

 investigated by obtaining a knowledge of the 

 conditions in which they take place, and of the 

 operations and changes in which they consist. 



The illustrious Harvey in his 51st Exercita- 

 tion expresses himself thus decidedly a sup- 

 porter of the theory of Epigenesis, " it is 

 plain that the chicken is built up by Epigenesis 

 or the additament of parts budding one out of 

 another;" but he does not admit that separate 

 powers, such as the "alterative or immutative, 

 formative, attractive, retentive, digestive, and 

 expulsive faculties, or those of apposition, 

 agglutination, and assimilative nutrition de- 

 scribed by Fabricius," can be distinguished in 

 the production of the chicken. He thus limits 

 our knowledge of the subject in the 54th 

 Exercitation : " But as in the greater world 

 we say Jovis omnia plena, all things are full of 

 the Deity, so also in the little edifice of a 

 chicken, and all its actions and operations, 

 digilus Dei, the finger of God or the God of 

 nature doth reveale himself." " A more sub- 

 lime and diviner artificer (than Man is) seems 

 to make and preserve man ; and a nobler agent 

 than a cock doth produce a chicken out of the 

 egge. For we acknowledge our omnipotent 

 God and most high Creator to be every where 

 present in the structure of all creatures living, 

 and to point himself out by his workes ; whose 

 instruments the cock and hen are in the gene- 

 ration of the chicken. For it is most apparent, 

 that in the generation of the chicken out of the 

 egge, all things are set up and formed, with a 

 most singular providence, divine wisdom, and 

 an admirable and incomprehensible artifice." 

 " Nor can these attributes appertain to any but 

 to the Omnipotent Maker of all things, under 

 what name soever we cloud him ; whether it 

 be the mens divina, the divine mind with 

 Aristotle, or anirna mundi, the soul of the 

 universe with Plato; or with others natura 

 naturans, Nature of nature herself; or else 

 Saturnus or Jupiter with the heathen, or rather 

 as befits us, the Creatour and Father of all 

 things in heaven and earth ; upon whom all 

 animals and their births depend : and at whose 

 beck or mandat, all things are created and 

 begotten."* 



3. Spontaneous generation of animals. In 

 this introductory view of the function of gene- 

 ration, it may "be proper shortly to inquire 

 whether a regular affiliation from parent to 

 offspring be an indispensable condition for the 

 continuation of the species of every kind of 

 animal, a question somewhat speculative in 

 its nature, but of considerable interest in rela- 

 tion to some of the general doctrines of physio- 

 logy, as well as closely connected with our 

 present subject. It has already been stated in 



* Anatomical Exercitations concerning the Ge- 

 neration of Living Creatures. London, 1653, 

 p. 310 et seq. 



general terms that origin by generation and the 

 power of reproduction are characteristics be- 

 longing to all organized bodies whether of the 

 vegetable or animal kingdoms. The existence 

 of life implies the sequence of decay and death, 

 or in other words, those varied operations and 

 changes which together constitute the living 

 state continue to occur in each organized body 

 for a limited period only : they sooner or later 

 undergo a gradual alteration, are less regularly 

 performed, and ultimately entirely cease in 

 death. But although every individual belong- 

 ing to the organized kingdom of nature is 

 necessarily subject to death, the species of each 

 plant and animal never becomes extinct, but 

 is continued upon earth in an undeviating suc- 

 cession of generations. The origin of a mineral, 

 on the other hand, is wholly independent of 

 any pre-existing body of its own kind ; and, 

 in the mineral kingdom, all those bodies are 

 held to belong to the same species which agree 

 in external form, physical properties, and 

 chemical constitution. The mineral owes its 

 first origin, as its subsequent increase, to the 

 simple union of its component particles ; but 

 the successive generations of every species of 

 organized bodies constitute an uninterrupted 

 chain extending from the time of their first 

 creation, and in which the formation of every 

 new link that is added depends on its tem- 

 porary attachment to that which preceded it. 

 So fixed, indeed, is the law of continued 

 reproduction of organized bodies, that many 

 naturalists have, in the absence of more definite 

 distinctive characters, adopted the circumstance 

 of reproduction as the only certain means of 

 determining what individuals ought to be 

 regarded as belonging to one species. 



While most naturalists readily admit the 

 correctness of the above-mentioned general 

 law, some are inclined to hold that it is not 

 universally applicable, and that there are excep- 

 tions to it both in the vegetable and animal 

 kingdoms of organized nature. It is among 

 the simplest kinds of plants and animals that 

 these exceptions are conceived to exist, and 

 more particularly among cryptogamic plants 

 of the nature of mould, small microscopic 

 animalcules formed in infusions of decaying 

 organic matters, and the Entozoa which live in 

 the bodies of other animals. These living 

 productions are supposed by some to arise in- 

 dependently of others of the same kind, nearly 

 in the manner of minerals, by the aggregation 

 of their component molecules, with this diffe- 

 rence, that these molecules are of an organic 

 kind. This sort of production without parents 

 has been termed Spontaneous Generation. It 

 has also received at different times various 

 other appellations, such as equivocal, doubtful, 

 primitive, original, and heterogeneous gene- 

 ration. 



At one time it was a common belief among 

 scientific men as well as the vulgar that 

 many animals might be produced by sponta- 

 neous generation, as for example, the numerous 

 insects or their larvae infesting putrid sub- 

 stances, various kinds of 'worms (Annelida), 

 and Molluscous animals, as well as even 



