342 R. A. KOCHER 



the result of exercise. Luxemburg (3) described a breaking up 

 of the chromatic bodies into granules, and Dolley tried to recon- 

 cile these contradictions by regarding the hyperchromatism as a 

 result of moderate activity, and the hypochromatism the result 

 of excessive activity or exhaustion. They find that both stages 

 may be present in the same animal simultaneously. Other 

 changes, such as wandering of the nucleus toward the periphery 

 of the cell (Magini (11), Lambert (10), Vas (9) ), rapture of the 

 nuclear and cell membranes (karyolysis and karyorhexis) have 

 been described. Dolley noted thirteen stages of cell change 

 from hyperchromatism to disintegration or death of the cell, 

 corresponding to the degrees of moderate activity up to com- 

 plete exhaustion. Eve (12), in a study of sympathetic nerve 

 cells, concludes that "there are usually some small differences 

 before and after stimulation, but these are nearly all inconstant 

 and generally reversible. Such divergence in the results is not 

 so surprising when we stop to consider the complicating factors 

 necessarily attending these experiments, such as, (1) difficulty 

 of separating the effects of normal activity from unavoidable 

 shock or injury to the nervous system in killing the animal (the 

 nervous system 'does not 'die' as soon as the heart stops beating); 

 (2) postmortem changes ensuing between the time of death and 

 complete penetration of the tissue by the fixing agent due to the 

 action of autolytic enzymes present in all tissue; (3) varying 

 chemical action of fixing agents; for example, formaldehyde coag- 

 ulates protein by combination w'th the amino groups, alcohol 

 by dehydration, sublimate by formation of salts, etc.; (4) the 

 solvent action of materials used in fixation and in imbedding, 

 for example, alcohol, xylol, paraffine ; (5) varying effects of chemi- 

 cal reaction between basic or acid dyes used in staining and the 

 different cell structures; (6) effect of subjecting tissue to tempera- 

 tures of 50° to 54° in the paraffine oven for a period of several 

 hours. 



In the present series of experiments I attempted as much as 

 possible to minimize the formation of artefacts, having in mind 

 the above mentioned considerations. It was hoped that by 

 using special care in the handhng of material, the use of im- 



