88 METHYLEN BLUE, AND OTHER ANILINS. 



iJc.j vi, 4, 1889, p. 422). Mayer's experiments were made 

 contemporaneously with those of Dogiel, cover much the same 

 ground, and give the same results. Mayer stained tissues for 

 about ten minutes in a 1 : 300 or 400 solution of methylen 

 blue in 0'5 per cent, salt solution, rinsed in salt solution, and 

 put up in the glycerin-picrate of ammonia mixture given 

 above, 119. He finds it may be stated that by this method 

 all the essential results of a nitrate of silver impregnation may 

 be produced by means of methylen blue. The images are either 

 positive or negative. In stratified epithelia and in endothelia 

 (for instance, in the testicular canals of the rat, in the 

 vascular system, in smooth muscle) cement-substance is 

 stained. In the cornea, ground-substance is stained, giving a 

 negative image of the corneal corpuscles ; and in like manner 

 a negative image is sometimes obtained of the intra-sarco- 

 lemmar nerve-endings in striated muscle of frogs and rats. 

 But methylen blue sometimes, as does sometimes silver 

 nitrate, gives positive images of the cornea. If the stain be 

 brought about by injection of the colour into the vascular 

 system, the positive impregnation is the more frequent ; 

 whilst if it have been brought about by the immersion of 

 the cornea, a negative image is more frequently obtained. In 

 medullated nerves, striking images of the cruciform figures in 

 the constrictions of Kanvier are obtained, just as with silver 

 nitrate. 



To sum up, almost any reaction that can be obtained with 

 chloride of gold, or with nitrate of silver, can be obtained 

 with methylen blue, and with much greater ease and 

 certainty. 



122. Other Uses of Methylen Blue. Methylen blue is also 

 used, chiefly in conjunction with other colouring matters, for 

 staining fixed and hardened tissues, especially preparations of 

 central nervous system. These uses will be described in their 

 proper places. 



B. Other Anilins (Plasma and Ground Stains). 



123. Bleu Iiumiere is stated to be a plasma stain not affecting nuclei. 

 I have not been able to make out whether it is identical with Parma blue, 

 which is one of the numerous toluidin blues. If it is, Frey recommends a 

 solution in water of 1 : 1000, in which tissues stain in a few minutes, and 



