LECTURE 11. 65 



immediately to be put in motion by it. Of 

 the nature of the organization subservient to 

 these motions, we are ignorant. We know 

 not whether they may arise from organs 

 formed purposely to produce them, or from 

 all the neighbouring parts being joined in 

 consent to occasion this effect. It seems 

 probable, however, that the power is ana- 

 logous to the irritability of muscles." 



Next are exhibited the nutritive fluids 

 both of vegetables and animals, and also 

 the fatty substance which makes so consi- 

 derable a part of the body in the latter class, 

 because all their different structures must be 

 formed from these nutritive materials. The 

 nutritive fluids, or blood of animals, and the 

 sap of some vegetables spontaneously coa- 

 gulate; but in other vegetables, the addition 

 of acetate of lead is necessary to produce 

 coagulation. The nutritive fluid, or blood 

 of insects, and the lower kinds of animals, 

 is shewn to be colourless, with the ex- 

 ception of that of some worms which have 

 red blood; and that in reptiles and fish, 

 the red colour which is so generally con- 



