Of NilTURAL HISTORY. ^15 



parts. As thefe organic particles are fimilar to the body it* 

 felf, their union with the different parts augments its fize, 

 without changing its figure. To unfold an embryo or germ, 

 nothing more is requifite than that it contain, in miniature, 

 a body fimilar to the fpecies, and be placed in proper cir- 

 cumftances for the acquifition of frefh organic particles to 

 increafe its fize and unfold its members. Hence nutrition, 

 developement, and reproduction, are all effects of the fame 

 caufe. 



This account of the nutrition and growth of organic bodies 

 has the appearance of an ingenious theory. But an atten- 

 tive reader will eafily perceive, that it contains no other in- 

 formation, than that animals and vegetables are nourifhed 

 and grow by the intervention of the nutritious particles of 

 food. This is a fact univerfaliy known and admitted. But 

 we are ftill as ignorant as ever of the mode by which this 

 myfterious operation is performed. 



Other authors have fuppofed that the brain is a large 

 gland ; that the nerves diflributed over the whole body are 

 the duels or canals of this gland j and that the principal ufe 

 of the brain is to fecrete nutritious matter, and to tranfmit 

 it by the nerves to the various parts of the fyflem, in order 

 to expand the different organs of which it is compofed, or 

 to repair the wafte they may have fufFered from labour and 

 other caufes. 



This theory prefuppofes that the nerves are tubular, and 

 contain a fluid : But both of thefe circamfiances have hith- 

 erto eluded the refearch of the ableft anatomifts. Befides, 

 the learned and indefatigable Doctor Monro, in his Nervous 

 SyReniy has rendered it highly improbable that the nerves are 

 the inftruments of nutrition. The Doctor reafons in the 

 following manner. On comparing different animals, he re- 

 marks, we find no correfpondence between the fize of their 

 brain, the rapidity of their growth, or the quantity of nourifh- 



