152 THE CELL DOCTRINE. 



ment, botfi in portions of its substance, producing 

 changes in shape, and in its entire mass, resulting 

 in changes of position. The former, and probably, 

 also, the latter, may have for its object the ob- 

 taining of pabulum, as is seen in the amoeba, when 

 it embraces by its protrusions a particle of nutri- 

 tive matter. These movements are less decided in 

 the cells of the higher animals, yet they are of con- 

 stant occurrence, as in pus and white corpuscles, and 

 when thus occurring they are spoken of as " amoeboid 

 movements." Allied or identical with this second 

 class of movements, are those of undoubted occur- 

 rence in white blood-corpuscles, first observed by 

 Addison,* Waller,t and Cohnheim,:j: whereby these 

 cells have been seen migrating from the bloodvessels. 



* Addison, Physiological Researches, London, 1841. 



f Waller, London, Dublin and EdinBurgh Philosophical Maga- 

 zine, vol. xxix, 1846, pp. 271 and 398. 



J Cohnheim, Ueber Entzilndung, und Eiterung, Virch. Arch. 

 Bd. xl, 1867, p. 1. 



