217 



Using tissue cultivation as a morphological and anatomical 

 method, it is still greatly limited by uncertainty in the 

 classification of the many cell types. As we have learned 

 now, the shape of the cells cannot be employed in the 

 classification. The morphology of the tissue cells may 

 change according to the mechanical conditions of the culture 

 medium (Uhlenhuth) ^^^). Epithelial cells in vitro may 

 appear polygonal, s({uamous. thin and elongated, fusiform 

 like fibroblasts and so on. The only and best way of distin- 

 guishing between the various cells in vitro, is, as suggested 

 by C o n g d o n i^^) to trace the outgrowth back directly 

 to their source in the parent tissue. For this purpose 

 sectioned cultures are necessary. The interrelation and the 

 structures of the tissues generally disappear a short time 

 after explantation. Tubules can be seen to grow out from 

 kidney to begin with or solid processes may grow as a 

 loose mesh (Lewis and Lewis) 3-^3) Most explants con- 

 tain several types of cells that migrate out into the medium, 

 some of wliich are rather eas}^ to identify. 



Nerve fibres from the central nervous system have 

 been observed by Harrison ^is) 219) jn his pioneer work, 

 where he showed that the regeneration of the axis cylinder 

 is a kind of protoplasmic movement, and that from the 

 neuroblasts of H i s. hyaline threads grew out which in- 

 creased in length by means of ameboid movements. Later 

 B u r r o w s 27)^ I n g e b r i g t s e n -' ^ ). Levi 329)^ Lewis and 

 Lewis 3^2) have observed the same thing. M a t s u m o t o 

 described the growth of sympathetic nerves. I n g e b r i g t- 

 s e n 272) studied the degeneration processes of the axis 

 cjdinder in vitro. M a r i n e s c o and Mine a ^oi^oo) investi- 

 gated in large dishes the growth of the axis cylinders from 

 spinal ganglia of young cats and rabbits in plasma. 



Endodermal membranes from the cells lining the 

 alimentary' tract and allantois were studied by L e w i s and 

 Lewis 350) and Lambert 289), The identification of these 



