IOS HOW TO WORK 



alkaline colouring fluids only. Solutions of an acid reaction may be 

 employed if the germinal matter be rendered alkaline in the first 

 instance by soaking the texture in a weak solution of ammonia. I 

 have prepared some beautiful specimens as follows :- An alkaline 

 solution was injected into the vessels, and after allowing twelve hours 

 or more for the tissues to become thoroughly permeated, the finest 

 Prussian blue fluid, see part V, was introduced. The latter passed 

 into the very substance of the germinal matter, which was tinged 

 much more deeply than the surrounding substance. The liver cell 

 may be thus impregnated with the blue in every part. It seems pro- 

 bable that by prosecuting more detailed enquiries in this direction, 

 we may learn something concerning the physical arrangement of the 

 matter constituting the formed material. Specimens prepared in this 

 way enable us to prove the unsoundness of the old notion concern- 

 ing the supposed cell wall and cell contents ; but in endeavouring to 

 draw correct inferences regarding the natural arrangement of the 

 parts prepared in this way, it must not be forgotten that the alkaline 

 ammonia may have effected alterations in the formed material, and 

 modified its structure in an important manner. 



197. Process of Staining followed by the Rev. Lord S. C. Osborne. 

 -Welcker was, I believe, one of the first observers to employ a 

 solution of carmine for the purpose of staining the nuclei of tissues, 

 and Gerlach was an early and most successful advocate of this plan. 

 It has been, but I think wrongly, stated, that Gerlach was the first 

 who employed this process. The date of Gerlach's work is 1858 

 (Mikroskopische Studien aus clem Gebiete der Menschlichen Morpho- 

 logic. Erlangen). But in June, 1856, the Rev. Lord S. G. Osborne 

 showed that nuclei were more deeply tinged by carmine than other 

 parts of the cell. (Vegetable Cell Structure and its Formation, as 

 seen in the early stages of the Growth of the Wheat Plant). See also 

 the plate accompanying this paper (Trans. Mic. Soc., vol. V, pi. IV, 

 1856). Lord Osborne allowed the plants to grow in the carmine 

 solution. The growing parts were stained most successfully. 



i8. Gerlach's Method of staining. Gerlach used first a con- 

 centrated solution of carmine in ammonia, and placed the sections 

 of brain and spinal cord previously hardened by chromic acid, in the 

 carmine fluid for from ten to fifteen minutes. They were then well 

 washed in water for some hours, and treated with acetic acid. The 

 water and acid were removed by immersion in alcohol. The sections 

 were afterwards mounted in Canada balsam. Gerlach found that 

 dilute solutions (two or three drops of the ammoniacal solution of 

 carmine to an ounce of water), and maceration for two or three days, 

 afforded better results. 



