APPENDIX 323 



of hydrogen added just before use. This has been recommended 

 for invertebrate tissues. 



Dogiel recommends for the nerve-endings in Herbst corpuscles 

 the following methods: (i) Sections of the waxy edge of the 

 beak or palate of a young duck are cut free-hand ; they are 

 moistened with ^ to J p.c. methylene blue in salt solution ; 

 covered up and warmed at 35 C. for 5 to 10 minutes; then 

 examined ; if the nerve-endings in the Herbst corpuscles are not 

 stained, a drop of methylene blue is added, and the preparation 

 warmed for a few minutes more. If the sections are not then 

 stained, others are made, (ii) Warm "25 to '5 p.c. methylene blue 

 is injected into the circulation, in 20 to 30 minutes the pieces of 

 tissue are exposed to air, placed in ammonium picrate solution 

 for to 1 hour, in 5 to 10 p.c. ammonium molybdate in water 

 for 12 to 18 hours, then washed, dehydrated and cut. 



Neutral red can be used like methylene blue (except for 

 fixation), i.e. for injection into blood vessels or adding a tissue 

 exposed to air ; in the latter case it must be very dilute to avoid 

 staining the nucleus ; granules only should be stained. 



Most granules in mammals are stained orange red. (In 

 neutral water, red; in weak alkali, yellow orange.) 



212 



