MODERN METHODS OP EXAMINATION. 61 



ous elements, and for spreading out thin and delicate tis- 

 sues or sections, are indispensable. Pipettes, or glass 

 tubes, one end of which can be covered with the end of 

 the finger, may serve to convey a drop of fluid or a small 

 specimen from a bottle. 



Preparation of Loose Textures. If the formed elements 

 of tissue do not combine in a solid mass, it is only neces- 

 sary to place a small quantity on a glass slide and cover 

 it with a plate of thin glass. If the elements are too close 

 for clear definition under the microscope, a drop of fluid 

 may be added. The nature of this fluid, however, is not 

 a matter of indifference. Some elements are greatly 

 changed by water, etc., and it becomes important to con- 

 sider the fluid which is most indifferent. Glycerin and 

 water, one part to nine of water, will serve well for most 

 objects. Animal tissues are often best treated with aque- 

 ous humor, serum, or iodized serum. A weak solution of 

 salt, 7.5 grains chloride of sodium to 1000 grains of dis- 

 tilled water, serves for many delicate structures. (See 

 section on Fluid Media.} 



Preparation by Teasing. A minute fragment of tissue 

 should be placed in a drop of fluid on a slide, and torn or 

 unravelled by two sharp needles. This is accomplished 

 more easily after maceration, and sometimes it is neces- 

 sary to macerate in a substance which will dissolve the 

 connecting material. This picking or teasing should be 

 slowly and accurately performed. Beginners often fail 

 of a good preparation by ceasing too soon, as well as by 

 having too large a specimen. The most delicate manipu- 

 lation is required to isolate nerve-cells and processes. 



Preparation by Section. A section of soft substance may 

 be made with a sharp knife or scalpel, or with a pair of 

 scissors curved on the upper side. A section cut with the 

 latter will taper away at the edges so as to aflbrd a view 

 of its structure. 



