THE CELL DOCTRINE. 53 



It has absorbed materials of nourishment for them 

 while in a state of development, and has passed 

 them off after they, have been fully formed, or have 

 arrived at a stage of growth when they can be de- 

 veloped by their own powers. 



" Centres of nutrition are of two kinds, — those 

 which are peculiar to the textures, and those which 

 belong to the organs. The nutritive centres of the 

 textures are in general permanent. Those of the 

 organs are in most instances peculiar to their em- 

 bryonic stage, and either disappear ultimately or 

 break up into the various centres of the textures of 

 which the organs are composed. 



" A nutritive centre, anatomically considered, is merely 

 a cell, the nucleus of which is. the permanent source of 

 successive broods of young cells, which from time to time 

 fill the cavity of their parent, pass off in certain 

 directions and under various forms, according to the 

 texture or organ of which their parent forms a part." 



Prof. Goodsir does not fail to state in the first para- 

 graph of his paper, that with many of these centres 

 anatomists have been for some time familiar, but 

 further remarks, that with few exceptions they have 

 looked upon them as embryonic structures. He al- 

 ludes in a note to the observations of Bowman and 

 Barry, the former on " Muscle," and the latter " On 

 the Corpuscles of the Blood," in Philosophical Trans- 

 actions, respectively, of 1840 and 1841, and states in 

 a second note that " for the first consistent account 

 of the development of cells from a parent centre, and 

 more especially the appearance of new centres within 

 the original sphere, we are indebted to .Martin 



5* 



