Thf. Identification of Intracellular Structures. 95 



account in the reading of the above classification. The key to the 

 difficulty lies in differentiation ; possibly all embryonic cells would 

 fall under the above classification. One of the greatest difficulties 

 is to ascertain whether the given cell granule is a living plastid- 

 like body, or merely a dead granule, and many of the so-called 

 oxyphile and basophile granules have only been studied in alcohol 

 and acetic acid fixatives, which give deceptive and entirely useless 

 results from this present point of view (Leishman and Jenner). 



The Mitochondeia and Golgi Apparatus in Stained 



Sections. 



The mitochondria and Golgi apparatus (figs. 1-3) never clearly 

 appear in stained sections prepared by such methods as fixation in 

 corrosive acetic, Gilson, picro-nitric, Bouin, Carnoy or Flemming- 

 with-acetic acid, and staining in Ehrlich's hsematoxylin and eosin, 

 toluidin-blue and eosin, paracarmine and borax carmine. Though 

 the mitochondria and Golgi apparatus are properly fixed by formalin, 

 Miiller, Flemming-without-acetic acid, Champy, Altmann, etc., they 

 will rarely appear visible in stained sections which have been pre- 

 pared in Ehrlich's hsematoxylin or carmine stains, or in fact in 

 any of the current laboratory stains used for general zoological 

 purposes. The mitochondria and Golgi apparatus may appear 

 visible in sections fixed in formalin, Miiller, etc., and stained in 

 Altmann's acid fuchsin-picric acid, iron-hsematoxylin, Benda's 

 alizarin and crystal- violet, etc. The Golgi apparatus rarely 

 becomes visible after any of the above methods, and to study it 

 one must use more specialized 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. 



The Golgi apparatus was first discovered by the Italian worker 

 after whom it is named, and was independently observed by Cajal. 

 Both Golgi and Cajal and their pupils worked principally upon 

 the "apparato reticolare interne," or Golgi apparatus of the 

 nerve ganglion cells of vertebrates. They used exclusively silver 

 nitrate or metallic impregnation methods. The Golgi apparatus of 

 nerve-cells has been studied exhaustively by workers in every 

 country, and new technical improvements have enabled observers 

 to use the Golgi and Cajal silver methods with fairly uniform 

 success. Besides these few silver methods for demonstrating the 

 Golgi apparatus in nerve-cells, Kopsch (5) has perfected an osmic 

 acid method which shows precisely the same structures by a shorter 

 and easier method (see below). Within the last few years Weigl 

 iil), Hirschler(5, '20), Pappenheimer (it*), Sjdvall {26), and myself 

 {17) and others have applied the silver and osmic methods, or 



H 2 



