302 GOLGI BODIES ETC. 



or objects left for days or weeks in chrome or osmium, can be 

 washed out overnight or longer. This hint with regard to failure 

 to stain properly, in haematoxylin or fuchsin may enable the 

 beginner to trace the fault to its source. Often, however, the stain 

 itself is bad. 



Washing is best carried out under the tap by covering the 

 vessel with gauze, held on by a rubber band. Minute objects w^ash 

 out more quickly and can be done by changing distilled water by 

 means of a pipette until the objects are properly washed. 



689. Difficulties and Faults in Techniques for the Cytoplasmic 

 Inclusions. It is important for beginners not to leave out the 

 Aoyama or Da Fano methods in favour of the Weigl or Kolatchew : 

 the reason for this is that failure of the latter methods (so far as 

 the Golgi apparatus is concerned) is sometimes complete while 

 the preparations may appear quite good. Failure may be brought 

 about by various factors; some we understand partly, some 

 not at all. For example, occasionally specimens of commercial 

 osmium tetroxide will not impregnate the Golgi apparatus ; in 

 some cases this is caused by not washing out the chrome fixative 

 sufficiently ; but this is not the only cause, as in Weigl's corrosive 

 sublimate method failure is also sometimes complete. Therefore, 

 as a control on these osmic methods, Aoyama or Da Fano methods 

 should be used. 



It should be unnecessary to point out that the pieces, or animals 

 used, should not be too big, and the dishes, capsules or phials 

 should be properly cleaned. When washing out under the tap it 

 is necessary to make sure that the water will run overnight. One 

 cannot counterstain osmicated preparations of the Weigl or 

 Kolatchew type unless one has carefully treated the sections in 

 permanganate of potash and oxalic acid, or in hydrogen peroxide. 

 One may, of course, stain the nuclei in acid neutral red (§ 710), but 

 one cannot stain the mitochondria properly unless bleaching has been 

 done. It is possible to get interesting preparations from pieces of 

 animals which have been killed for dissection, but one cannot 

 depend on such material for research work. For the best results 

 anim^als which have just been killed without ether or chloroform 

 should be used. 



For oogenesis studies and in protozoology we believe that the ultra- 

 centrifuge is indispensable. It is better not to take up the study 

 of granules in eggs or protozoa, unless it is possible to have some 

 material ultra-centrifuged. Sometimes one can make quite good 

 preparations of mitochondria and Golgi bodies from material 

 which has been fixed in 10 per cent, formalin and left in it for 

 months. But if the formalin has disintegrated badly, such 

 material is useless. In the formalin silver methods, fresh formalin, 

 and newly-made solutions of silver nitrate, and new reducer are 

 recommended. The commercial formalin used for museum work, 



