162 JOHN STEPHENS LATTA 



ranging from newborn to individuals of fifty-six days postpartum; 

 that is, to a time after the intestinal tonsils had assumed an adult 

 structure. Tissues from older individuals at less frequent in- 

 tervals, were also obtained, up to an age of about two and one-half 

 months. 



Helly's fluid (Zenker-formalin) was used almost exclusively 

 as a fixing reagent, as did most recent investigators of hemato- 

 logical problems. With it, in the writer's experience, is given the 

 best general fixation, without in any way interfering with de- 

 sired subsequent staining with the compound blood stains. In 

 a few instances a fixer suggested by Downey ('15) was used. 

 This was a 0.9 per cent normal salt solution saturated with 

 HgCl2, to which 10 per cent of formalin was added at the time of 

 using. This gave results apparently equally as good as Helly's, 

 but there being no advantages held over the latter, it was seldom 



used. 



The tissues were all imbedded in paraffin and cut in sections 

 from 5 to 7 At in thickness. 



The stain used most extensively in this study w^as Hasting 's 

 modification of the Nochts-Romanowsky blood stain. Wright's 

 blood stain was also used to some extent, but the Hastings- 

 Nochts combination was equally as selective as Wright 's for cells 

 of the blood series, and gave a more brilliant, intense and a 

 sharper nuclear stain. The sections were first stained six to ten 

 minutes in the concentrated stain, and then removed, without 

 washing, to a solution of the stain diluted one-half with dis- 

 tilled water for ten to fifteen minutes. The sections were then 

 differentiated and dehydrated in 95 per cent and absolute alcohol, 

 cleared in several changes of neutral xylene, and mounted in 

 neutral xylene damar. 



A combination composed of a 1 per cent solution of eosin in 

 methylic alcohol, followed by a weakly alkaline, aqueous solu- 

 tion of methylene blue (Gage, '17), was found to be almost 

 as selective a stain for blood cells as Hastings-Nochts, and to 

 gwe a still more brilliant, sharp picture. Therefore, this stain 

 was quite extensively used. The sections were carried imme- 

 diately from 95 per cent alcohol into the 1 per cent methyl alco- 



