2652 Journal of Applied Microscopy 



Commendation of Worcester's Formol-sublimate-acetic Mixture. 



This fixing fluid designed by Professor Worcester for the study of karyo- 

 kinesis in teleost eggs, and lately described in this journal by Dr. Pearl, can 

 scarcely be too highly commended for general work. For eight years I have 

 used it more than any other fluid, and on account of its faithful fixing, its rapid 

 action, and the good staining properties of the tissues fixed with it I consider it 

 one of the most valuable fluids which we possess. It has the further advantage 

 of being cheap, easily prepared and perfectly stable. I have used it for a great 

 variety of objects, including a large number of Protozoa, Hydra, Lumbricus, 

 and various other worms, mussel, crayfish, and the tissues of all classes of verte- 

 brates, and have uniformly obtained good results with it. It has given better 

 results than any other fluid on amphibian embryos and teleost eggs, and is excel- 

 lent for the study of reproductive glands, ciliated epithelia, and for both chro- 

 matin and cytoplasm of dividing cells. The surface, form, and appearance of 

 embryos is preserved with remarkable fidelity. The time of fixation and harden- 

 ing may be very short, but tissues are not injured when left in the fluid for hours. 

 They are less brittle than when fixed in Flemming's fluid, and seem to keep better 

 in alcohol. 



The failure of sublimate to fix cell membranes is corrected in this mixture 

 (by the formol ?). When amphibian embryos are stained entire with borax 

 carmine the cell outlines are of course indistinct. But if sections are stained 

 with haemalum and afterstained by means of a little acid fuchsin added to the 

 strong alcohol used for dehydration, cell boundaries come out very clearly. This 

 fluid is not to be recommended for nerve work. It does not fix medullary sheaths 

 and apparently medullated tracts offer an obstacle to the fixation of other portions 

 of the central nervous system. J. B. Johnston. 



West Virginia University. 



A Model for Demonstrating the Structure of the Kidney 



Tubule. 



It is usually difficult to explain by the use of figures alone the structure of 

 the end of the kidney tubule and the relations of the blood vessels to it. For 

 this purpose I have used for several years the model here described. 



With clay, a model of the end of the tubule can be made by moulding a 

 cylindrical portion with enlarged spherical end. This can then be cut away so 

 as to show the character of the tubule, the relative thickness of the wall of the 

 duct and the capsule, and the invaginated end. If now the middle of a piece of 

 the flexible " cord " used for electric drop lights be held in the flame of a bunsen 

 burner the insulation will be burned away and the constituent wires will separate, 

 giving a fairly accurate model of the way an artery breaks up into capillaries 

 and then unites again to form a vein. If desired, one end may be colored red 

 and the other blue, to give the conventional arterial and venous colors. With 

 this a glomerulus can be constructed and put in place on the clay model. On 

 the side of the " vein " another bit of the insulation is removed to represent the 

 capillaries around the secretory portion of the tubule. 

 Vassar College. AaroN L. Treadwell, 



