246 CHAPTER XVIII. 



1 : 400 for the study of the endothelium of vessels by injec- 

 tion. 



EODGET (Arch. dePhysiol., 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 HEETWIGS take, for marine animals, a 1 per cent, 

 solution (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. 



TOURNKUX and HKRKMANN (ROBIN'S Journal de V Anat., 1876, 

 p. 200) for the epithelia of Invertebrates employed a solu- 

 tion 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 90 per cent. 



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

 of nitrate of silver of known strength, and adds ammonia to 

 it until the precipitate that is formed just redissolves, then 

 dilutes the solution until it contains from 0'75 to 0'50 per 

 cent, of the salt. 



This ammonio-nitrate solution is intended principally for 

 the impregnation of the endothelium of vessels by injection, 

 but can also be used for the impregnation of membranes by 

 pouring on. It has the advantage of impregnating absolutely 

 nothing but endothelium or epithelium ; connective tissue is 

 not affected by it. It is also said to give a sharper localisa- 

 tion of the stain than the ordinary solutions. 



DKKHUYSEN (Anat. An?.., iv, 1889, No. 25, p. 789; Zeit. f. 

 iciss. Mik., vii, 3, 1890, p. 351) has applied to tissues of 

 terrestrial animals the method of HAKMKK for marine animals 

 (see below, 343). For details see previous editions. 



REGAOD (Journ. Anat. et Phys., xxx. 1894, p. 719 ; Zeit. f. 

 u-'iss. Mik., xii, 1, 1895, p. 74) recommends for the study of 

 lymphatics a process devised by RENAUT, for the details of 

 which see also previous editions. 



340. Other Salts of Silver. ALFEROW (DuvAL, Precis, p. 230) recom- 

 mends the picrate, lactate, acetate, and citrate, as giving better results than 

 the nitrate. He employs them in solutions of 1 : 800, and adds to the 

 solution employed for staining a small quantity of the acid of the salt 

 taken (10 to 15 drops of a concentrated solution of the acid to 800 c.c. of 

 'the solution of the salt). The object of the free acid is to decompose the 



