GROWTH OF TISSUES OF THE CHICK EMBRYO 



69 



stable condition as far as coagulation is concerned. On this 

 account, plasma which would coagulate at summer temperature in 

 twenty minutes or less has been most satisfactory for the present 

 work. The diops on the side coagulate very rapidly at 39° C. and 

 hold the tissue firmly. When it is lacking in this ability to clot 

 spontaneously at high temperature, it often remains fluid for 

 several hours and the clots about the tissue lack uniformity and 

 firmness with a corresponding disturbance in uniformity of growth. 

 No plasma over four days old was used for any experiment. 



GENERAL DESCRIPTION OF THE EXPERIMENTS 



The different tissues of the chick embryo, when isolated and trans- 

 planted to a coagulable plasma, show marked activity of prolifera- 

 tion and growth for a considerable period of time. In the present 

 set of experiments, the tissue of the central nervous system was es- 

 pecially studied, other tissues being used as controls for further 

 proof in the identification of cells and nerve fibres. 



The tissues most active, as shown by table 1, have been tht 

 nervous and mesenchymatous tissues. Muscle cells show little 

 evidence of growth. 



TABLE 1 



Whole neural tube 



Hemisected neural tube 



Teased pieces of neural tube. . 



Heart 



Myotomes 



NUMBER OF 

 PHEPAKATIONS 



NUMBER OF PREPARATIONS SHOWING 



Muscle cell I Nerve fibres | Mesenchyme 



64 



47 

 27 

 40 

 12 



3 



23 



21 











64 

 47 

 27 

 36 

 12 



The first appearance of cellular activity in any of the above 

 tissues appeared between the second and the twelfth hours and 

 generally not later than the end of the first day. This early cell- 

 ular growth was always identified as mesenchymatous in origin. 

 The growth of nerve and muscle cells generally begins to show 

 between the second and sixth da\ after transplantation. The 

 cellular activity continued from six to eight days in most of the 

 preparations. Some few remained active as long as twelve days. 



