108 METALLIC STAINS. 



out the nuclei, provided the impregnation has not been over- 

 done. 



It should be noticed that impregnations only succeed with 

 fresh tissues, and cannot be made to succeed with tissues pre- 

 served in any way. 



199. Silver Nitrate. The Solutions to be Employed (RANVIER) . 

 The solutions generally employed by E/anvier vary in 

 strength from 1-300 to 1'500. Thus 1'300 is used for the 

 epiploon, pulmonary endothelium, cartilage, tendon, whilst a 

 strength of T500 is employed for the study of the phrenic 

 centre, and for that of the epithelium of the intestine. For 

 the impregnation of the endothelium of blood-vessels (by in- 

 jection) solutions of 1'500 to 1'800 are taken. 



M. DUVAL (Precis , p. 229) recommends solutions of 1, 2, or 

 at most 3 per cent. 



V. RECKLINGHAUSEN used, for the cornea, a strength of 

 from 1 400 or 1 500 (Die Lymphgefdsse, &c., Berlin, 1862, 

 p. 5). 



ROBINSKI (Arch, de PhysioL, 1869, p. 451) used solutions 

 varying between O'l and 0'2 per cent., which he allowed to 

 act for thirty seconds. 



REICH (Sitzb. d. wien. Acad., 1873, iii, Abth., April; 

 Zeit. f. wiss. Mik., i, p. 397) takes solutions of from 1 600 

 to 1 400, for the study of the endothelium of vessels by 

 injection. 



ROUGET (Arch, de PhysioL, 1873, p. 603) employed solutions 

 as weak as 1 750 or even 1 1000, exposing the tissues to 

 their action several times over, and washing them with water 

 after each bath. 



The HERTWIGS take, for marine animals, a 1 per cent, solu- 

 tion (Jen. Zeit.f. Naturk., xvi, pp. 313 and 324). 



The HOGGANS (Journ. of Anat. and Physiol., xv, 1881, p. 477) 

 take, for lymphatics, a 1 per cent, solution. 



TOURNEUX and HERMANN (ROBIN'S Journal de I' Anat., 1876, 

 p. 200) in their fine studies on the epithelia of invertebrates, 

 employed a solution of 3' 1000 strength, and in some cases 

 weaker solutions. The tissues were allowed to remain in the 

 silver-bath for one hour, and were washed out with alcohol of 

 36 strength. 



HOYER (Arch. f. mik. Anat., 1876, p. 649) takes a solution 



