334 CYTOLOGICAL METHODS. 



chondria and Golgi apparatus (nebenkern) of male cells distinctly 

 violet. Both methyl violet 5 B (Griibler) and methyl blue in aqueous 

 solutions will stain the mitochondria. Bismarck brown gives a less 

 clear picture. See under these dyes in Part I. 



705. Cajal, Golgi, and Da Fano Silver Nitrate Methods for the 

 Golgi Apparatus. For vertebrate tissue Cajal or Golgi, and for 

 invertebrate tissue Cajal and Da Fano methods are a great aid to 

 research on the cell. Every cytologist is recommended to master 

 either Cajal's or Da Fano's method. These methods will be found 

 in the neurology section ( 844, 849). 



706. Differentiation between Cell Inclusions. It is frequently 

 somewhat difficult to distinguish between the various categories 

 of cell inclusions. In this section we have provided a series of tables 

 intended to act as a tentative guide to the interpretation of the 

 various images got by representative cytological techniques. These 

 tables are based on work carried out on animals of most orders, 

 but it would be injudicious for the researcher to depend upon them 

 implicitly, because many exceptions are met with, and the personal 

 factor is to be taken into consideration. The use of such tables, 

 if made with several methods and in conjunction with a careful 

 study of the origin and morphology of any doubtful cell body, will, 

 however, provide reliable evidence for identification. Another 

 warning must be given never try to ascertain the nature of 

 granules in developing eggs without first studying the oogenesis 

 of the animal in question. Eggs after spawning or laying are difficult 

 objects to study by these methods, and even the most experienced 

 worker is unable to give a valuable interpretation until he has 

 worked at the oogenesis. It should also be remembered that there 

 are periods in the development of the cell during which the mito- 

 chondria are often able to resist becoming dissolved in lipoid solvents, 

 these periods are in the early spermatogonium in some animals, 

 and during the last stages of spermatogenesis (spermateleosis) in 

 all animals, and sometimes in large oocytes. See also the work of 

 REGAUD, Arch. (TAnat. micr., xi. 



Nota Bene. With regard to the oil used for clearing and im- 

 bedding, it should be pointed out that all these tables are based 

 on preparations cleared and imbedded in xylol, which occasionally 

 tends to extract lightly osmicated fat. Vegetable oils like cedar 

 wood oil seem to be less active in this way. I have not found that 

 chrome-osmicated fat, or " Kopsched " fat, is extracted either by 

 xylol or xylol-balsam. See also 768. 



