414 SOME OTHER HISTOLOGIOAL METHODS. 



refraction of the fat being thus eliminated, nuclei and cytoplasm may be 

 studied to far greater advantage than in the usual preparations. 



788. Granule-cells (" Plasmazellen " and "Mastzellen"). In 

 1874 there were described by WALDEYER (Arch. f. mik. Anat., Bd. xi) cer- 

 tain special cells existing between the bundles of connective tissue, besides 

 the flat cells, and lymphatic and fat cells. They are large round cells contain- 

 ing large granules ; Waldeyer called them plasma cells (" Plasmazellen "). 

 Later on, EHELICH (ibid., xiii, 1877) distinguished in the same tissue and in 

 other places certain cells containing large granules, which have a superficial 

 resemblance to Waldeyer's plasma cells, but which differ from them in 

 staining reaction (Verhandl. Berl. Physiol. Ges., January 17, 1879 ; Reichert 

 u. Du Bois Reymond's Arch., 1879, p. 166). Ehrlich named these food 

 cells (" Mastzellen"), intending to express thereby the opinion that these cells 

 are derived from fixed connective-tissue cells by a transformation brought 

 about by exalted nutrition. 



If (KoRYBUTT-DASZKiEWicz, Arch. f. Mik. Anat., xv, 1878, p. 

 7) frogs be kept for two months (in snmmer) without food,, 

 then placed in a reservoir of running water and well fed for 

 four weeks, " plasma-cells " will be found in abundance, 

 especially in the neighbourhood of the nerves. 



It is a pretty general character of these elements that they 

 take the stain of anilin colours and retain it on treatment with 

 alcohol with greater energy than other tissue cells. And 

 further (at least so far as regards the true Mastzellen of 

 Ehrlich) that in successful preparations they show the nucleus 

 unstained, the general mass of cytoplasm unstained or but 

 slightly coloured, and, in the cytoplasm, the characteristic 

 granules very intensely stained. 



The staining reactions of the granules are very similar to 

 those of bacteria. In order to distinguish them from these 

 it may be observed that the stain of anilins is removed from 

 the granules, but not from bacteria, by treatment with a 

 weak solution of carbonate of potassium, (SQUIRE, Methods and 

 Formula, p. 46). EHELICH distinguishes no less than five kinds 

 of granulations, recognisable by certain differences in their 

 staining reactions. It will be remembered that according to a 

 generally accepted principle of classification, due to Ehrlich 

 (Arch.f. Anat. u. Phys., Phys. Abth., 1879, pp. 167 and 572), 

 anilin dyes are divided into two chief classes, viz. the " basic " 

 dyes, or those in which the colouring matter plays the part of 

 a base combined with a colourless acid; and the " acid " 

 dyes, in -which the colouring matter plays the part of an acid 



