54 PROTOPLASM. 



in three different states matter about to become living, 

 matter actually living, and matter that has lived. The last, 

 like the first, is non-living, but unlike this it has been in the 

 living state, and has had impressed upon it certain characters 

 which it could not have acquired in any other way. By 

 these characters we know that it has lived, for we can no 

 more cause matter artificially to exhibit the characters of the 

 dried leaf, the lifeless wood, shell, bone, hair, or other tissue, 

 than we can make living matter itself in our laboratories. 



Cells are not like Bricks in a Wall. 



Cells forming a tissue have been compared to bricks in 

 a wall, but the cells are not like bricks, they have not the 

 same constitution in every part, nor are they made first and 

 then embedded in the mortar. Each brick of the natural 

 wall grows of itself, places itself in position, forms and 

 embeds itself in the mortar of its own making. The whole 

 wall grows in every part, and while growing may throw 

 out bastions which grow and adapt themselves perfectly to 

 the altering structure. Even now it is argued by some 

 that because things, like fully formed cells, may be made 

 artificially, the actual cells are formed in the same sort 

 of way an argument as forcible as would be that of a 

 person, who after a visit to Madame Tussaud's exhibition, 

 seriously maintained that our textures were constructed 

 upon the same plan as the life-like wax figures he had 

 seen there. 



Every one who really studies the elementary parts of 

 tissues and investigates the changes which occur as the 

 germinal matter passes through various stages of change 

 .y. / 



f / 



7 



--. '' 



r 





