APPENDIX. 357 



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

 these fluids the tissue should be mounted. 



c. Normal saline solution. 



This is prepared by dissolving 6 grm. of sodium 

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

 water. This is for some tissues rather better than 

 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 such 

 pieces as do not contain the parts required should 

 be thrown away. 



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



