1 88 Regeneration 



He is inclined to attribute this increase in the rate of 

 cell division to the stretching of the epithelial cells, and 

 he is supported in this reasoning by the observation that 

 the larger the wound the more rapid the process of 

 healing. 1 During wound healing the mitoses first 

 increase markedly in the old epithelium. With the 

 closure of the wound a sudden fall in the mitoses takes 

 place. The closure of the wound causes an increase in 

 the number of epithelial rows over the defect. This 

 increase is therefore reached at an earlier period in the 

 larger wound since the process of mitosis is more rapid 

 here. Leo Loeb thinks that the pressure of the epithelial 

 cells upon each other leads to a rapid diminution in the 

 mitotic proliferation. 2 



'Spain, K. C., and Loeb, Leo, Jour. Exper. Med., 1916, xxiii., 107; 

 Loeb, L., and Addison, W. II. F., Arcli.j. Entwcklngsmech., 1911, xxxii., 

 44; 1913, xxxvii., 635. 



2 The excessive formation of epithelial cells in the healing of wounds 

 has led the older pathologists to the generalization that if something is 

 removed in the body an excessive compensation will take place. The 

 formation of antibodies has even been explained on this basis by Weiggert 

 and Ehrlich in their side-chain theory. As a matter of fact, this generali- 

 zation is entirely incorrect and in regeneration of starfish, actinians, 

 flatworms, annelids, and possibly in all forms the reverse is true; e. g. t 

 if we cut off the anterior half of the body in Cerianthus less is reproduced 

 than was cut away namely only tentacles and the mouth, but not the 

 missing piece of the body. Weiggert's conception of regeneration was 

 probably based on the phenomenon of the healing of wounds, but the 

 excessive epithelium formation in this case is not the expression of a 

 general law of regeneration but of the peculiar mechanical conditions 

 which lead to mitoses. It would be a very strange coincidence indeed if 

 a theory of antibody formation based on such an erroneous generaliza- 

 tion should be correct 



