REGENERATION. 453 



and functional regeneration takes place, so that voluntary movements again 

 occur. Vaulair observed in frogs and Masius in dogs first motility, then sensi- 

 bility, return. Regeneration of the spinal ganglia did not take place. According 

 to Stroebe a formation of fibers takes place in a small, limited area at the site 

 of injury to the spinal cord of the rabbit, but not complete regeneration of the 

 actual spinal tissue. 



6. In some glands the regeneration of their cells during normal activity is 

 exceedingly active, for example the sebaceous glands, the mucous follicles of the 

 stomach, the glands of Lieberkuhn, the uterine glands, the mammary glands 

 during pregnancy; in others regeneration is less active. The removal of consider- 

 able portions of various glands is not followed, as a rule, by regeneration, while 

 after injury of glands regeneration of the affected parts does not take place if 

 suppuration occurs. Regeneration of the biliary passages, the bile-duct, and of 

 the pancreatic duct, is remarkable. After injury of the liver Tizzoni and Colluci, 

 as well as Griffini, observed the regeneration of liver-cells and biliary passages 

 even beyond the normal limits of the liver. Pisenti reports similar observations 

 upon the kidney. 



After injury to the liver Podwisotzky observed the deficiency disappear com- 

 pletely through partial multiplication of the liver-cells and partial hyperplasia of 

 the epithelial cells of the biliary passages, which are likewise transformed into true 

 liver- tissue (resembling the embryonal development of the liver) . Ponfick extir- 

 pated even three-quarters of the liver, and regeneration set in within a few days 

 after the operation and was complete in the course of a few weeks. 



According to Philippeaux and Griffini regeneration may take place after partial 

 removal of the spleen, according to Laudenbach, in the dog, even after almost 

 complete removal. After mechanical injury to the secretory cells of certain glands 

 (liver, kidney, salivary, mammary, Meibomian) hyperplasia and division of adja- 

 cent cells take place for the purpose of regeneration. The nipple of which half 

 has been extirpated undergoes regeneration. 



7. Of the connective tissues, cartilage, providing its perichondrium remains 

 intact, appears to regenerate by division of the cartilage-cells, although, probably, 

 loss of tissue is most frequently replaced by connective tissue. 



8. After incised wounds of tendons reunion takes place through the agency of 

 the tendon-cells themselves. These multiply considerably by utilizing the matrix 

 for the formation of cells and by mitotic division of the latter. If the extrem- 

 ities of the divided tendon are widely separated, granulation-tissue forms for 

 the development of a cicatrix, as a result of marked reaction in the surrounding 

 connective-tissue tendon-sheath. 



9. The regeneration of bone is remarkable. If the articular extremity, together 

 with the adjacent portion of the bone, be resected, it may be regenerated, although 

 an appreciable shortening results. Pieces of bone that have been broken or sawed 

 off reunite if replaced; likewise teeth that have been removed and replaced in 

 the alveolus. An isolated piece of periosteum, even if transplanted to another 

 bone, gives rise to a piece of bone of corresponding size. Defects in bone are 

 readily filled by bony tissue if the periosteum be preserved. For this reason the 

 surgeon in resecting diseased bones carefully preserves the periosteum, in the hope 

 that the bone will regenerate from it. The medulla of bone may also regenerate. 

 The internal medullary membrane is capable, if transplanted, of producing bony 

 tissue in small amount from the osteoblasts present. 



If a bone, for example a long bone, has been fractured, a circular thickened 

 deposit, at first of rather gelatinous, vascular and cellular, later of firmer car- 

 tilaginous, character, forms from the periosteum upon the external surface at the 

 site of fracture the external callus. A similar process takes place at the same 

 time within the medullary cavity, which is thereby diminished in size internal 

 callus. These formations are due to cell-multiplication, in part from the perios- 

 teum, in part from the medulla and the bone-tissue itself. The callus generally 

 resembles tissue, and is often cartilaginous. 



In the external and internal callus calcification of the cartilage later takes 

 place, as well as the deposition of osseous lamellae, which, acting as rings, fix the 

 fractured extremities. Later (up to the fortieth day) a thin layer of the same 

 material forms between the fractured extremities, and this subsequently under- 

 goes ossification intermediate callus. With the final solidification of the latter, 

 the bony matter of the external and internal callus gradually disappears. Ex- 

 ternally, the swelling disappears, internally the medullary canal becomes again of 

 uniform size and the intermediate callus eventually acquires the same archi- 

 tecture as the adjacent portions. Bone-fractures toward which the course of the 



