294 



CELLS, TISSUES, AND ORGANISMS 



Figure 4. Drawing of longitudinal section of regenerate and stump 16 days 

 after amputation and two days after implantation of pieces of nerve taken 

 from opposite brachial plexus. The epithelium has grown inward to en- 

 capsulate the implants almost entirely. Note the continuity of the epithelial 

 sheets and their connections with the surface. In autotransplantation the 

 epithelial reaction subsides before the tissue is thrown out. H: humerus; I: 

 implant. Animal: IE 186. Bodian silver stain. Magnification: approximately 

 70 X. 



form an epithelial capsule. The outermost layer of the capsule thinned 

 and then separated, and in this way the implant was thrown out of the 

 blastema within one or a few days. During the encapsulation the 

 epidermis seemed to respond to the foreign body as it does to a bare 

 wound, by gliding as one associated structure over it. Scattered debris 

 was observed among the epidermal cells and the cells themselves 

 seemed loosely associated. Implants which excited the epithelium 

 maximally, among others, were pieces of paraffin and surgical cellulose 

 sponges, fragments of celloidin, crystals of chloretone, and surgical 

 thread. 



The normal amphibian epidermis also responds to implanted 

 foreign bodies, but much more slowly. We have observed that a num- 



