28 



CYTOMORPHOSIS 



muscular substance which breaks down after the injury. 

 The muscle fibers, however, contain also the so-called muscle 

 corpuscles, which are nothing more than little accumulations 

 of undifferentiated protoplasm, containing the nucleus, 

 Fig. 1 6. After the injury these corpuscles do not degenerate, 

 so that undifferentiated protoplasm remains from which the 

 new formation starts. The differentiated part of the muscle 

 disappears and there is in this case no question of a regressive 

 development. 



hd 



'y'-'ZjtAf-* 





, .•»<*' -••'"est. >^ 





Fig. 17. — ^Longitudinal section of the regenerating extremity of a young lobster 

 one day after amputation. There is formed at first a blood clot (bd) under which 

 the epithelial cells e, e', grow across to form the commencement of the new part. 

 Magnification 240. — After V. E. Emmel. 



The third example we will take from the lobster. If the 

 extremities of the larvae of this animal are cut off, the ex- 

 tremities will be newly formed. It was formerly assumed 

 that we had to do in such a case with a new regressive develop- 

 ment. The investigation made by Emmel ^° in my laboratory 

 has rendered the real history clear. The cells of the outer- 

 most layer of the skin in these larvae are undifferentiated ceUs, 

 which after the injury grow and spread over the wounded 

 surface. They then multiply and by their steady growth 



