NOTE ON THE MULTIPLICATION AND MIGRATION OF 

 NUCLEOLI IN NERVE CELLS OF MAMMALS. By W. Page 

 May and C. E. Walker. (With Two Plates.) 



(Beceived for publication 29th February 1908.) 



Methods. 



The tissues mainly employed in the observations here described were the 

 Oasserian and cerebro-spinal ganglia of rats, rabbits, cats, monkeys, and 

 chimpanzees. Other nerve cells were also similarly examined, notably 

 those of the red nucleus, cerebral cortex, and other large motor and sensory 

 cells throughout the central nervous system, and similar phenomena to 

 those described in the present communication were also found to obtain 

 in them. Further details bearing on this subject we hope to bring forward 

 later. The animals were, with one or two exceptions, young adults. 



Absolutely fresh material was fixed in Flemming's fluid (strong formula), 

 or a modification of Zenker's fluid (G. Arnold's). It was dehydrated by 

 increasing the percentage of alcohol by 10 per cent, at each stage, and 

 the greatest care was taken to prevent any possibility of maceration by 

 shortening the time between removing the material from the fixative and 

 getting it into 70 per cent, alcohol. Imbedding was carried out at a 

 temperature of 45° Cent., and this process did not occupy more than an 

 liour and a half ; thus any undue exposure to heat was avoided. The 

 manipulation used in mounting and staining was according to the strictest 

 eytological methods. Various staining methods were employed and all 

 gave similar results, though it was found that particular methods rendered 

 certain points in the observations clearer than others. The main processes 

 adopted were : — 



A. Basic f uchsin, followed by methylene blue and Unna's orange tannin. 



B. Safl'ranin, followed by methylene blue and Unna's orange tannin 

 (Breinl method). 



C. Thionin counterstained wnth Bordeaux red, etc. 



In the present communication the term " nucleolus " is used in its 

 strictest sense, i.e. it is restricted to the structure which has sometimes 

 been called the "true nucleolus," whilst such bodies as the so-called 

 " chromatin nucleoli " contained in the nucleus are definitely excluded.^ 



' Cf. Wilson, "The Cell in Development and Inheritance," p 34; Macmillan, 

 London and New York, 1904. Walker, "The Es.sentials of Cytology," pp. 12 and 13; 

 Constable, London, 1907. 



