432 BIOLOGY: GENERAL AND MEDICAL 



power to resist the external forces with which they have 

 to contend. 



The less imperative the nutritional requirements of 

 any tissue, the more apt it is to withstand absorption 

 in the new environment. While it persists, new tissue 

 may grow in and about it so that when its final disap- 

 pearance takes place it may not be missed. In some 

 cases the transplanted tissue survives exactly as in 

 autoplastic operations. Thus it is that in Carrel's experi- 

 ment upon the replacement of a blood vessel by the em- 

 ployment of a part of a vessel from another animal, the 

 transplanted fragment is able to perform its function 

 even though it be kept on ice or otherwise for some 

 days before being put in place. 



The inherent vitality of any tissue has something to 

 do with its ability to persist after transplantation, the 

 differences in different tissues being shown by the experi- 

 ments of Ribbert who transplanted a variety of different 

 tissues to the lymph nodes. Epithelial cells so trans- 

 planted shortly died; fragments of salivary -glands per- 

 sisted for a longer time, the glandular cells changing 

 to a cuboidal type, and the duct epithelium becoming 

 flat; liver tissue so transplanted underwent a central 

 necrosis, but the surface remained alive for some weeks 

 until the epithelial cells were destroyed by the com- 

 pressing effect of the connective tissue; kidney tissue 

 was so transformed that the cells of the convoluted 

 tubules came to resemble those of the straight tubules 

 and the tissue to resemble that of the kidney of chronic 

 interstitial nephritis, after which it was gradually ab- 

 sorbed; when the skin was transplanted in such manner 

 that both the epiderm and cutis were included in the 

 graft, the cells continued to be nourished by their sub- 

 jacent tissue and spread out until they lined the space 

 into which the tissue was transplanted and a cyst was 

 formed. The transplantation of connective tissues some- 

 times fails, sometimes succeeds. The softer the tissue, 

 the sooner it is absorbed ; the denser the tissue, the longer 



