120 CELL THEORIES. 



important point to determine how far the passage 

 of substances through that membrane was the 

 result of mere osmosis, and how far it depended on 

 the action of some attractive power within. To the 

 school whose tendency was to refer everything to 

 the laws of dead matter, the cell-wall was a most 

 important agent ; to those on the other hand who 

 considered that to account for the formative changes 

 in living bodies the presence of another force must 

 be assumed, the nucleus as situated in the interior 

 seemed the source of vital actions. 



Moreover, in the absence of a defined know- 

 ledge of the protoplasmic element, the conception 

 of the nucleus was obscured by extending the 

 designation to bodies which ought not to be so 

 named. An instance of this may be found in 

 the case of connective-tissue-corpuscles. Many 

 years before Virchow's researches threw a light 

 on these structures, a corpuscular element was 

 recognized as present in connective tissue. It 

 was even taught by some to be the same ele- 

 ment as could easily be demonstrated as consti- 

 tuting, in a cellular form, a large part of the bulk 

 of fcetal connective tissue, and to be of the utmost 

 importance in its vital properties. But that element, 

 in the adult, was known only as it may be found 

 figured by Dr. Sharpey in 1848 (Quaint 'Anatomy,' 



