APPENDIX. NOTES. 401 



In other mineral bodies, as in white arsenic, which did 

 not exhibit the fibrils, he found oval particles about the 

 size of two molecules, which he conjectures to be primary 

 combinations of them : their motion, which was more vivid 

 than that of the simple molecule, consisted usually in 

 turning on their longer axis, and then often appearing to 

 be flattened. 1 The revolution of a body upon its axis, it 

 may be observed, implies the action upon it of two equal 

 conflicting forces, by the counteraction of which the revo- 

 lution is produced and maintained: the same action on 

 the longer fibrils 2 would keep them at rest. 



My motive for introducing a topic, which, at the first 

 blush, seems to have a very slight connexion with the 

 subject now before me, was a suspicion that sometimes 

 Mr. Brown's molecules may have been mistaken for 

 Infusory Animals. Comparing the oscillatory motion he 

 observed in them, and Carus' observation that the motions 

 of Infusories occasionally present the appearance of attrac- 

 tion and repulsion, 3 this suspicion seems to merit attention, 

 and to call for more close examination; and it may be 

 observed that the action of these two powers seems suffi- 

 ciently to account for the oscillatory motions of the mole- 

 cules, and takes away all idea of any spontaneity. With 

 regard to the Infusories this has been most satisfactorily 

 established in a former part of this chapter, 4 and this 

 clearly proves their animal nature, as do their modes of 

 motion, &c. 5 but when we recollect that they abound in 

 vegetable infusions, and that the more vegetables are 

 macerated, and as it were decomposed, the more numerous 

 are the animalcula that they appear to give out when 



1 Ubi supra. " Ibid. 11. 



3 Introd. to Comp. Anat. E. Tr. i. 45. 57. 



4 See above, p. 150. a /^. 1.53. 



