SECT. VII.] NECESSITY OF NERVES TO NUTRITION. 427 



For that wondrous force, which forms a foetus similar to the 

 parents, out of the semen of the male projected into the uterus, 

 and that part which the female contributes, whether it be an 

 ovum or semen — that force, I say, is not exhausted in the forma- 

 tion of a puny foetus,^ but continues active in it, and thus 

 carries forward the human body through all its phases of growth 

 and age, to the perfect state, fittingly replaces from the nutrient 

 material, the particles worn away and dissipated by the con- 

 tinual movements and operations of life, nay, regenerates in a 

 great measure portions of skin lost by violence, consolidates 

 wounds, forms the callus of bones, &c. To this are owing 

 those so-called efforts of nature, by which she attempts to 

 preserve health and remove disease. In some animals, as 

 lizards, for example, this vis structrix is so efficient, that it repro- 

 duces in them tails, extremities, and jaws, together with their 

 bones, muscles, vessels, and nerves.^ Eminent philosophers 

 readily perceived, that these and many other phenomena observed 

 in the animal organism, and also in the vegetable, can be 

 referred neither to the wisdom of a rational soul, nor to any 

 mechanical and physical laws as yet known ; and, consequently, 

 they have very properly termed that wonderful cause innate in 

 the animal and vegetable organism, the vital principle, inas- 

 much as to that, as a proximate cause, both animal and vegetable 

 owes its life ; which is also distinct from the thinking principle, 

 for it far excels this in wisdom, and is not subject to it, and 

 has higher faculties, than it has hitherto been agreed that 

 bodies possess. The vital principle is not some simple force, 

 but seems to be compounded of various unknown forces co- 

 operating together ; amongst which unknown forces so co-ope- 



and when injured, repairs it as much as may be. Very lately, also, Metzger, Professor 

 at Kbnigsberg, in the first volume of his work entitled ' Vermischte Medicinische 

 Schriften,' (Konigsberg, 1782,) weakens the force of the arguments adduced by 

 Haller in favour of evolution ; and in the supplement to the second volume, declares 

 his assent to the views of Blumenbach. He differs, however, in thinking that the 

 nisus formativus cannot be considered as distinct from the vis plastica of the ancients 

 and the vis essentialis of Wolff, since it so much resembles them ; so that the vis 

 essentialis is primary, and analogous to the vis vitalis of physiologists, which con- 

 stitutes life, both in animals and vegetables: secretion, nutrition, generation, and 

 reproduction, are portions, or rather branches, of this. 



' See Fasciculus ii of my ' Acad. Adnot.,' p. 31. 



^ See my * Comment, de System. Generat.* 



