XII.] 



ADENOID TISSUE. 



173 



acid, and the sections stained with eosiii-hsematoxylin and mounted 

 in balsam. 



(H) Observe some parts crowded with lymph corpuscles, but where 

 these are wanting, note the very fine network of fibres, with nuclei 

 here and there at the points of intersection (fig. 143). 



The lymph corpuscles may be got rid of by applying to a fresh 

 preparation a dilute solution of caustic potash which dissolves them. 



12. Pigment-Cells and Guanin-Cells. These may be studied 

 by pinning out on a frog-board one of the webs between the toes of 

 a frog (Lesson XIX. 11, e). 



(r/.) (Land H) Observe large, branched, corpuscles loaded with 



Leucocyte 



FIG. 143. Adcm^d Tissue. Human lymphatic 

 glunil. Picric acid and eosiu-heematoxylin. 



FlG. 144. Pigment and Gnanin-Cells of 

 Frog. A Contracted: B,C. Partially 

 relaxed pigment-cells. G Guairin 

 cells. 



black granules of melanin (fig. 144, B), also smaller black spots, 

 which are cells with their processes retracted. Every intermediate 

 stage between these two states may be seen. 



A permanent preparation is readily made by stripping off the skin 

 from the web of the toe of a dead frog, hardening it in alcohol, and 

 mounting in balsam. The web should be fixed in an extended 

 position before it is placed in the alcohol. 



In such a preparation, not only will pigment-cells be found, but 

 guanin-cells also, i.e.., small oval cells filled with white refractive 

 granules of guanin (fig. 144, G). To see the guanin-cells turn off 

 the light reflection from the mirror, when the granules in the guanin- 

 cells will appear bright and refractile on a black ground. 



For pigmcnted connective-tissue corpuscles from the choroid, see 

 Lesson on Eye. 



