EPITHELIUM. 343 



matol. u. Syphilis, 1892, 1, p. 303; Zeit. f. wiss Mik., ix, 

 1893, p. 356. 



Sections are easily made by the usual methods. The best 

 hardening agent for skin appears to be Muller's solution. 

 This was the conclusion of F. E. SCHULTZE in 1867 (Arch, f. 

 mik. Anat., p. 145), and it is that of TIZZONI, the author of 

 important researches on this organ (Bull, delle Sc. med. di 

 Bologna, 1884, p, 259), and of BEHN (Arch. f. mik. Anat., 

 xxxix, 1892, p. 581). Simple bichromate of potash solution 

 will do about as well. 



For glandular epithelium it is frequently better to employ 

 a chromic acid liquid, or osmic acid (see, for example, BANVIER, 

 loc. cit., p. 258, et seq.), or absolute alcohol (BLAUE, Arch. f. 

 Anat. u. Phys., 1884, p. 231) ; " Kleinenberg" is not so good. 



Prickle-cells and Intercellular Canals. Besides maceration, 

 which is one of the most important of the methods for the 

 study of these objects, impregnation may be useful. MITRO- 

 PHANOW (Zeit. f. wiss. ZooL, 1884, p. 302, and Arch. f. Anat. 

 u. Phys., 1884, p. 191) recommends the following process : 

 Wash with distilled water the tail of an axolotl larva ; put it 

 for an hour into 0'25 per cent, solution of gold chloride with 

 one drop of hydrochloric acid to a watch- glassful of the solu- 

 tion ; wash, and reduce in a mixture of one part of formic 

 acid with six parts of water. 



Macerating Media. For soft epithelia, mild macerating 

 agents, such as iodised serum, one-third alcohol, saliva, or 

 Schultze's mixture of saliva and solution of Miiller, or a 

 mixture of saliva with three to four volumes of physiological 

 salt solution (BizzozERO, Intern. Monatschr. f. Anat., 1885, p. 

 278) for hard epithelia, energetic dissociating agents, such 

 as 40 per cent, solution of caustic potash. 



MINOT (Amer. Natural., xx, 1886, p. 575 ; cf. Journ. Roy. 

 Mic. Soc., 1886, p. 872) recommends maceration for several 

 days in 0'6 per cent, solution of sodium chloride containing 

 O'l per cent, of thymol, which allows the isolation of the 

 epidermis of embryos, and is useful for the study of the 

 development of hairs. 



Another method, given by MITROPHANOW (see Zeit. f. wiss. 

 Mik., v, 4, 1888, p. 513), is as follows : An embryo of axo- 

 lotl is fixed for a quarter of an hour in 3 per cent, nitric acid, 

 and then brought into one-third alcohol. After an hour the 



