GOLGI BODIES ETC. 299 



prepared in Ehrlich's or Delafield's hicmatoxylin or carmine 

 stains, or in fact with any of the current laboratory stains used for 

 general zoological purposes. The mitochondria and Golgi appa- 

 ratus may appear visible in sections lixcd in formalin, Miiller, 

 etc., and stained in Altmann's acid, fuchsin-picric acid, iron- 

 hfematoxylin, Benda's alizarin and crystal-violet, etc. The Golgi 

 apparatus rarely becomes visible after an^^ of the above methods, 

 and to study it one must use more specialised methods ; to 

 study the Golgi apparatus and the mitochondria by routine 

 zoological laboratory technique is not possible, simply because 

 these methods will not demonstrate the bodies in question. 

 Nearly all of the older fixing mixtures contain either alcohol, 

 chloroform, or acetic acid, but the last few years of cytological 

 research have shown that the pictiu'c given by a fixing mixture 

 containing them is incorrect and inadequate, and one cannot 

 fail to be surprised at the improvement produced when these 

 reagents are omitted. Nearly all modern research on the 

 cytoplasm has to be carried out by using chrome formalin 

 or osmium fixatives, followed by iron-alum haematoxylin, 

 Benda's crystal-violet, or Altmann's acid fuchsin ; or by the 

 important Kopsch and Mann-Kopsch, and Ludford osmium 

 tetroxide methods ; or by the useful methods of Cajal, Golgi 

 or Da Fano's modification of Cajal, which consist of silver nitrate 

 impregnation following formalin fixation. Intra-vitam methods, 

 such as janus green, neutral red, or dahlia violet, are also used 

 extensively. The mitochondria are extremely fuchsinophile, 

 and after chrome-osmium fixation stain strongly in iron-alum 

 haematoxylin. The Golgi apparatus of somatic cells and of 

 ovarian cells rarely stains by these methods (Altmann or 

 Heidenhain) unmodified, although the Golgi apparatus of the 

 male germ cells nearly always stains in fuchsin or haematoxylin 

 after chrome-osmium or formalin fixation. 



In § 648 is a special article on fats and lipoids, and on methods 

 for their study ; on the following pages are set forth various 

 techniques for the investigation of definite cell organs known to 

 be partly lipoid in nature. The application of all these methods 

 to embryological study opens the way to a valuable field for 

 research. Fats or lipoids form a special part of almost all cell- 

 organs, as seems to be indicated by fixing tests, and so far as 

 we know such substances are always intimately associated with 

 protoplasm. ^Nlan}- of the lipoids appear to be able to form with 

 certain metallic salts or oxides such as CrOg, KgCrgOv, PtCl4, 

 OSO4, etc., compounds insoluble or only slowly soluble in alcohol 

 or such clearing oils as xylol, benzol, or chloroform ; this is one 

 of the several reactions which take place when a cell is fixed in 

 such a fluid as that of Hemming (without acetic acid), Champy, 

 or Altmann, and subsequently dehydrated and cleared. 



