82 METHYLEN BLUE, AND OTHER ANIL1NS. 



EHRLICH) to inject naethylen blue into the vascular system or 

 body-cavity of a living animal, wait a sufficient time for it to 

 take effect on the organ to be stained, then remove the organ 

 for further preparation and study. And there appears to 

 have been a belief with some workers that it was an essential 

 or at least a desirable condition to the production of the 

 stain that it should have been brought about by injection of 

 the colouring matter into the entire animal. It is now known 

 that this is immaterial, and that the reaction can equally well 

 be obtained by removing the organ and subjecting it to a 

 bath of the colouring matter in the usual way. So that treat- 

 ment with the colour by means of injection or by means of 

 immersion in a solution may be taken to be a matter of con- 

 venience only. 



117. The Solutions employed. The solutions used for injec- 

 tion are generally made in salt solution (physiological, or a 

 little weaker) ; those used for staining by immersion are made 

 either in salt solution or other "indifferent" liquid, or in pure 

 water. Very various strengths of solution have been em- 

 ployed. The earlier workers generally took concentrated 

 solutions. Thus AENSTEIN (Anat. Anz., 1887, p. 125) injected 

 1 c.c. of saturated solution into the vena cutanea magna of 

 frogs, and removed the organ to be investigated after the 

 lapse of an hour. BIEBERMANN (Sitzb. d. k. Akad. Wiss. Wien, 

 Math. Nat. Cl, 1888, p. 8) injected 0'5 to 1 c.c. of a nearly 

 saturated solution in O6 per cent, salt solution into the thorax 

 of crayfishes, and left the animals for from two to four hours 

 before killing them. MAYER (Zeit.f. wiss. Mik., vi, 4, 1889, 

 p. 423) took a strength of 1 : 300 or 400 of 0'5 per cent, salt 

 solution. This can be introduced into the system either by 

 means of a syringe or other injecting apparatus, or by auto- 

 injection through the heart. Even rabbits support this ope- 

 ration if artificial respiration be maintained. The solutions 

 of RETZIUS are of the same strength. But the tendency of 

 more recent practice is decidedly towards the employment of 

 weaker solutions. APATHY (Zeit. f. iviss. Mik., ix, 1, 1892, 

 pp. 25, 26, et seqq.} finds that it is not only superfluous, but 

 positively disadvantageous, to take solutions stronger than 

 1 : 1000. 



For staining by immersion similar solutions to those used 



