370 REGENERATION OF TISSUES. 



these cells proliferate and elongate to form lens fibres, so that the whole cavity of 

 the empty lens capsule is refilled. If much water be withdrawn from the body, 

 the lens fibres become turbid. [A turbid or opaque condition of the lens may 

 occur in diabetes, or after the transfusion of strong common salt or sugar solution 

 into a frog.l 



3. The blood-vessels undergo extensive regeneration, and they are regenerated in 

 the same way as they are formed ( 7, B). Capillaries are always the first stage, 

 and around them the characteristic coats are added to form an artery or a vein. 

 When an artery is injured and permanently occluded, as a general rule the part of 

 the vessel up to the nearest collateral branch becomes obliterated, whereby the 

 derivatives of the endothelial lining, the connective-tissue corpuscles of the wall, 

 and the leucocytes change into spindle-shaped cells, and form a kind of cicatricial 

 tissue. Blind and solid outshoots are always found on the blood-vessels of young 

 and adult animals, and are a sign of the continual degeneration and regeneration 

 of these vessels. Lymphatics behave in the same way as blood-vessels ; after 

 removal of a lymphatic gland, a new one may be formed {Bayer). 



4. The contractile substance of muscle may undergo regeneration after it has 

 become partially degenerated. This takes place after amyloid or wax-like degener- 

 ation, such as occurs not unfrequently after typhus and other severe fevers. This 

 is chiefly accomplished by an increase of the muscle corpuscles. After being com- 

 pressed, the muscular nuclei disappear, and at the same time the contractile contents 

 degenerate. After several days, the sarcolemma contains numerous nuclei which 

 reproduce new muscular nuclei and the contractile substance. In fibres injured by 

 a subcutaneous wound, Neumann found that, after five to seven days, there was a 

 bud-like elongation of the cut ends of the fibres, at first without transverse striation, 

 but with striation ultimately. If a large extent of a muscle be removed, it is 

 replaced by cicatricial connective-tissue. Non-striped muscular fibres are also 

 reproduced ; the nuclei of the injured fibres divide after becoming enlarged, and 

 exhibit a well-marked intra-nuclear plexus of fibrils. The nuclei divide into two, 

 and from each of these a new fibre is formed, probably by the differentiation of the 

 peri-nuclear protoplasm. 



5. After a nerve is divided, the two ends do not join at once so as to permit the 

 function of the nerve to be established. On the contrary, marked changes occur. 

 If a piece be cut out of a nerve-trunk, the peripheral end of the divided nerve 

 degenerates, the axial cylinder and the white substance of Schwann disappear. 

 The interval is filled up at first with juicy cellular tissue. The subsequent changes 

 are fully described in 325, 4. There seems to be in peripheral nerves a continual 

 disappearance of fibres by fatty degeneration, accompanied by a consecutive forma- 

 tion of new fibres (Sigm. Mayer). The regeneration of peripheral ganglionic cells 

 is unknown. V. Voit, however, observed that a pigeon, part of whose brain was 

 removed, had within five months reproduced a nervous mass within the skull, con- 

 sisting of medullated nerve-fibres and nerve-cells. Eichhorst and Naunyn found 

 that in young dogs, whose spinal cord was divided between the dorsal and lumbar 

 regions, there was an anatomical and physiological regeneration, to such an extent 

 that voluntary movements could be executed ( 338, 3). Vaulair, in the case of 

 frogs, and Masius in dogs, found that mobility or motion was first restored, and 

 afterwards sensibility. Regeneration of the spinal ganglia did not occur. 



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

 very active sebaceous, mucous, Lieberkiihnian, uterine, mammary glands during 

 pregnancy in others less. If a large portion of a secretory gland be removed, as 

 a general rule, it is not reproduced. A gland, if injured, and if suppuration follows, 

 is not regenerated. But the bile ducts ( 173) and the pancreatic duct may be 

 reproduced (171). According to Philippeaux and Griflfini, if part of the spleen 

 be removed it is reproduced ( 103). Tizzoni and Collucci observed the formation 





