244 Regeneration. 



of the keratogenous cells over the surface of the granulating papillae 

 and fleshy laminse of the persisting cutis (the latter the seat of 

 compensatory and sometimes regenerative changes) and the forma- 

 tion of a new protective layer over the denuded papillary surface 

 (Gutenacker). The first formed cells are pushed forward by suc- 

 ceeding new growth and form keratous tubules by arranging them- 

 selves in circles about the papillae ; later interpapillary keratous 

 substance is deposited in the intervals between the tubules as a yel- 

 low, perhaps soft and incompletely keratosed, and usually very 

 thick mass (cicatricial keratin). In parts where there are no 

 papillae the keratogcnous cells are arranged in irregular, superim- 

 posed layers. Operative denudations of the corium of the hoof 

 from five to ten square centimeters in area may be completely over- 

 grown by new horny substance in the course of from four to six 

 weeks. 



(For details cf. Lchrb. d. Cliinirgic, by Frohner, and /f M/feranfe- 

 heiten, by Gutenacker.) 



Regeneration, compensatory for losses of cylindrieal epithelium 

 upon mucous membranes, proceeds in the same way as the process 

 in the epiderm. The epithelial cells growing in from the periphery 

 over the surface of the lesion at first assume flat, then cubical and 

 finally cylindrical shapes and in appropriate cells it is even possi- 

 ble that the ciliated border will be reformed. The surface epithe- 

 lium of a wound of the gastric mucous membrane of a dog may be 

 completely reformed in from four to ten days. 



Regeneration of Glands. — Epithelium of glands is very irregular 

 in its regenerative ability. The epithelium of glands of the mucous 

 membranes corresponds histologically with that of the surface of 

 the membrane, as in the intestine or uterus ; and therefore in these 

 parts epithelial repair over cicatrices, ulcers and wounds may, be- 

 sides merely covering the surface of the lesion, sometimes also ap- 

 parently attempt gland formation in points of depression. The 

 epithelial cells formed in such cases grow from remnants of in- 

 volved glandular structures or from the uninvolved adjacent tissue 

 over the seat of the lesion. The depressions occur at the 

 expense of the young growing connective tissue or granula- 

 tion tissue which is being developed at the same time ; but the more 

 marked the retraction of the scar the less successful the glandular 

 reformation. Ponfick, Gluck and v. Meister in their interesting ex- 

 periments have pointed out in connection with regeneration of 

 the liver that after operative removal of a portion of the hepatic 

 tissue from rabbits, rats and dogs a remarkable regenerative activity 



