Tlic Ideniijication of Intracellular Structures. 107 



Glycogen {Animal Starch). 



(a) Not preserved in water fixatives 'whicli contain no OsO^, or 

 very small quantities of alcohol. 



(b) Preserved in 95 to 100 p.c. alcohol, or Carnoy's fluid. 



(c) Eeddish brown in iodine-iodide of potassium staining 

 method. (See below.) 



(d) Eed in Best's carmine stain. 



(e) It should be noted that different specimens of tissue have 

 glycogen with differing water-solubility, but watery fixatives must 

 be avoided. See de Waele's method (acetate of copper — OsOi), 

 Mann (1), p. 29'6. 



Sections (h), (c), and (d) are sufiiciently specific. 



General Notes. — If the preservation is chrome-osmium, Golgi 

 apparatus, mitochondria, and often yolk may go black with iron- 

 haematoxylin. Benda's alizarin and crystal- violet is not specific for 

 mitochondria, as has been stated ; it may stain a violet shade Golgi 

 apparatus, and often insect yolk especially, and the chromatoid, 

 neutral-red, or isolated granule of insect and other spermatids. 



It would be a mistake to consider that the above tests act as 

 reliably as chemical tests for inorganic substances ; they are only 

 suited to those workers who have had some experience in fixation 

 and staining, and it should be borne in mind that all the elements 

 of the cytoplasm are closely allied and chemically difficult to dis- 

 tinguish. It is also worth while to mention that if one given 

 method fails to demonstrate a desired body, some small modification, 

 such as a longer or shorter time in the fixative or a strengthening 

 or dilution of the latter, may produce the necessary effect. 



Smears — Protozoa and Testes. 



All the Protozoa (16) so far studied have mitochondria, and in 

 the only case appropriately examined there was a Golgi apparatus 

 present (^0). I have little doubt that every protozoan will be 

 found to have a Golgi apparatus. With regard to the above Tables 

 in their bearing on the Protozoa, it has been found that in Schaudinn 

 and Bouin smears neither mitochondria nor Golgi apparatus show. 

 In fact, even using F.W.A.* or other mitochondrial fluids followed 

 by iron-hsematoxylin, it is a matter of difficulty successfully to 

 demonstrate mitochondria in smears even of metazoan cells. In 

 cases where pieces of parasitized gut, liver with cysts, etc., can be 

 immersed in the fluid (F.W.A., Kopsch, etc.), and the protozoan 

 parasites examined subsequently in sections, the above Tables should 

 be found to agree with the reactions of the cell organs in their 



* Flemming's strong formula without acetic acid. 



