I2 8 CELL THEORIES. 



of the specially developed properties. In muscular 

 fibre it appears to be lost altogether.] 



Probably the greatest difficulty in conceiving 

 of the origin of differentiated textural elements 

 from common corpuscles is to settle the relation of 

 epithelial to other corpuscles, and on that subject 

 it is not easy to give an opinion. In particular, 

 the phenomena of skin-grafting, including the 

 stimulus given to the growth of skin over a whole 

 ulcer by the presence of grafts of minute size, 

 might even suggest the possibility of a sexual 

 distinction between the corpuscles of the graft and 

 those among which it is planted. At all events, 

 the microscopy of skin-grafting is worthy of study, 

 and the utility of the practice affords evidence that 

 all the less differentiated corpuscles are not capable 

 of producing, at least without assistance, all other 

 kinds of corpuscles. [Evidence of this is especially 

 to be seen in the circumstance that the most 

 effective grafts are those which completely dis- 

 appear before being succeeded by a transparent 

 pellicle which spreads ; and also in the well-ob- 

 served fact that improvement in an ulcer to which 

 grafts have been successfully applied is not con- 

 fined to the spots where they have been placed.] 



It must be kept in mind that the corpuscular 

 mass of the embryo becomes early divided into 



