APPENDIX. 357 



clot in a vessel, to obtain the serum. In one of 

 these fluids the tissue should be mounted. 



c. I^ormal saline solution. 



This is prepared by dissolving 6 grm. of sodium 

 chloride (pure if obtainable) in 1000 o.c. of distilled 

 ■water. This is for some tissues rather better thau 

 the "75 p.c. solution which is often used, but in 

 many cases there is nothing to choose between the 

 two solutions. * 



d. Iodized serum. 



Iodine is sometimes added to serum to preserve it, so 

 that it may be at hand when required ; serum thus 

 iodized is, however, far less a 'normal' fluid than 

 the others. It may be prepared by dropping a few 

 crystals of iodine into fresh serum, and shaking 

 occasionally. The fluid should be of a light brown 

 colour. Instead of serum the amniotic fluid of the 

 cow may be taken. 



Teasing. 



Be careful to take a small piece only : it should be 

 viewed with a low power before teasing, to ascertain 

 the general relation of the parts, and hence to guide 

 the teasing : thus, if it consists of parallel fibres, 

 with one needle fix the piece at one corner and draw 

 the other needle through it in the direction of the 

 fibres ; in teasing out to shew special objects, e.g. 

 ganglion-cells, the arrangement of the parts should 

 be particularly noticed under a low power, and snch 

 pieces as do not contain the parts required should 

 be thrown away. 



In teasing, it is important to place the slide on an 



