15] PROTEOCEPHALIDAE — LA RUE 15 



the grades. Sometimes after the corrosive acetic fixation 5% formalin 

 was used for a preservative with uniformly excellent results. 



Sections were cut 5 to 10 micra thick for the study of histological 

 detail and 20 micra when grosser morphological details were sought. 

 The sections were stained with haematoxylin mixtures, either Delafield's 

 haematoxylin or Mayer's haemalum, and decolorized in the manner 

 approved for these stains. Methods of staining in toto followed by sec- 

 tioning were used with great success at times. For this purpose Ehr- 

 lich's acid haematoxylin much diluted with 50% alcohol gave the best 

 results. For a contrast stain eosin in 95% alcohol was used on the sec- 

 tions. Acid fuchsin also in 95% alcohol was sometimes used effectively. 



Preparations in toto were much used and were found to be of great 

 value in mapping out the relationships of the organs of the proglottids. 

 Frequently these methods showed everything to be desired except the 

 histology of the organs. In some cases even histological details were 

 well revealed by these methods. The stains which were tried for staining 

 in toto were Mayer's paracarmine, Grenadier's borax carmine, some 

 alcoholic cochineal mixtures, Mayer's haemalum, Delafield's haematoxy- 

 lin, and Ehrlich's acid haematoxylin. None of the carmine or cochineal 

 stains were very successful for none of them show the boundaries of 

 cestode structures sharply. The parenchyma in which the genital organs 

 lie always retained too great an amount of these stains to permit a clear 

 view of the genital organs themselves. The haematoxylins, however, 

 usually gave wonderfully clear, sharp pictures of the genital organs. 

 It was at times possible to work out such minute structures as vasa 

 efferentia almost in their entirety from such preparations in toto. The 

 three haematoxylin stains were found to be about equally good. 



In using these stains it was the practice to dilute the stain with the 

 proper diluent. Relatively large quantities of the diluted stain were 

 used for each lot of material. The stain was permitted to act over night 

 (10 to 15 hours) at room temperature. The excess of the stain was then 

 removed by washing in distilled water and the tissue passed through the 

 grades of alcohol to 70% where it was decolorized rapidly by adding 

 hydrochloric acid to make a 0.5 to 1.0% solution. The object was to 

 remove the stain from the peripheral tissues at a rapid rate and mean- 

 while leave the stain in the deeper lying tissues. In this method the 

 duration o'f the acid bath is usually short depending upon the size of the 

 piece and the character of the stain taken by the tissue, and upon the 

 character of the tissue itself. In general it is desirable to decolorize 

 until a light reddish blue stain remains and until many of the internal 

 structures can be distinguished while the tissue is still in the alcoholic 

 medium. When in the judgment of the operator the proper stain is 



