I20 GEORGE FRED SUTHERLAND. 



Function der Ernahrung; ausserdem nehmen sie zerfallende 

 Gewebsproducte auf und assimiliren dieselben, um sie an anderen 

 Orten wieder zu deponiren. Niemals werden sie selbst zu 

 fixen Gewebszellen, weder in der Bindesubstanz noch sonst wo. 



"2. Sammtliche der in Frage kommenden Gewebe der Am- 

 phibien und Reptilien sind im Stande, sich zu regeneriren; 

 entweder direct aus ihren Elementen, oder aus einer Matrix, so 

 lange diese Matrix unverletzt ist. Als Matrix fiir die Epidermis 

 ist das Rete Malpighii, fiir das centrale Nervensystem das 

 Epithel des Centralcanales, fiir die Muskulatur die Muskel- 

 korperchen zu betrachten. 



"3. Zuerst regeneriren sich Epithel und Bindegewebe; beides 

 scharf getrennt, urspriinglich aus gleichartigen Zellen bestehend, 

 die sich spater dififerenziren," 



There remains the further problem of the stages in the process 

 by which the old organs at the cut surface replace their lost 

 parts. Two distinct kinds of changes take place in this process, 

 (i) degenerative and (2) regenerative. First the injured cells 

 at the cut edge degenerate. Then follows regeneration proper, 

 or the formation of the new organ from the remaining elements 

 of the old. 



There are three ways in which regeneration proper might 

 take place, (i) The cells at the cut edge of each organ by 

 dividing might extend outward, and in time form the completed 

 organ: (2) the cells in front of the cut edge might wander back- 

 ward; and (3) the cells in front of the cut edge might divide in 

 situ and push backward the more distal cells. These possible 

 methods of regeneration will be made clearer by a diagram of 

 that part of the hollow neural tube extending forward from the 

 cut (Fig. i). If (i) (division of cells at the cut edge) were the 

 method of regeneration, we should find after the operation that 



Anterior ^ Cut 



a mwffi4^uwmwwwwmwmwwmimmpm4ti4WWffl4^ 



B ED C A 



Fig. I. Diagram, explained in the text. 



the cells at the cut surface A , or from A to C, are dividing rapidly 

 while from C to B about the normal number of cells is dividing. 



