132 A. RICHARDS. 



Fixatives. To show exactly the various effects of the fixatives 

 used and to show that the results obtained are not due to the 

 exclusive use of one reagent, I wish to give here a detailed state- 

 ment of those effects. 



In his work on Moniezia Child used some eleven fixatives of 

 which the most successful were Hermann's fluid, saturated 

 aqueous solution of corrosive sublimate, and Graf's chrom- 

 oxalic mixture. I, therefore, used these three fluids and in 

 addition certain others which my own experience suggested. 

 These were, as previously stated, Flemming's and Zenker's 

 fluids, Zenker plus an excess of acetic acid, and formol-sublimate. 

 Dr. King fixed some of my first lot of material in her modification 

 of Zenker's fluid. I have no hesitation in saying that this fluid 

 gives the best results for Moniezia of any which I have tried. 

 Subsequently, I myself have used this solution with equally 

 satisfactory results. 



The results of my experiments with the various fluids follow. 

 Chrom-oxalic is not, I find, a good general fixative for Moniezia. 

 The general cytoplasmic structures, parenchyma, etc., are not 

 well preserved and the achromatic substances of the nuclei are 

 dissolved out. The chalk bodies 1 also are not retained. Testis 

 cells are more satisfactorily fixed, as are also the cleavage cells 

 and young embryos. But in the case of spermatozoa and the 

 young female germ cells the mixture is not successful. Nuclei 

 are everywhere swollen, but in these special cases they are also 

 distorted. I should not care to trust any results based on the 

 observation of early oogonia in my chrom-oxalic material. 

 Many of Child's results are founded on chrom-oxalic material; 

 doubtless he had greater success with this mixture than I did. 



Hermann's is a good fixative for the developing germ cells, 

 both male and female; for parenchyma the results are slightly 

 less satisfactory. Nuclear contents are well preserved in this 

 solution much better than in the preceding one. It also gives 

 a good preparation of the cuticle. With Flemming's, Hermann's 

 shares the drawback of fixing the calcareous bodies so that they 



J As part of their "generic diagnosis" Stiles and Hassal give this statement, 

 "Calcareous bodies absent from the parenchyma." They, however, studied only 

 sublimate material. 



