356 APPENDIX. 



generally better to do so. Such specimens may be 

 prepared in various ways. 



A few parts of the body, e.g. the kidney, are sufficiently 

 thin to allow sections to be cut free-hand with a 

 razor ; one section should be mounted without adding 

 any fluid, another in a normal solution, and a third 

 should be teased out in a normal solution. 



With structures too yielding to cut sections, e.g. the 

 villi of the small intestine, a piece may be snipped 

 off with scissors ; in the same way a good specimen 

 may often be obtained from the edge of a lobule of 

 a gland : in some cases, e.g. the coat of an artery, a 

 strip may be torn off with forceps; and in the case 

 of membranous structures, a piece may be pinned 

 out over a hole in a stage, the gastric glands and 

 pancreas of some animals for example may be thus 

 observed. 



The knowledge gained by the examination of such 

 specimens is essential to thoroughly understanding 

 the appearances presented by the tissue after the 

 action of reagents. 



There are certain fluids which, when fresh, cause very 

 slight changes in the tissues; they more or less 

 resemble the fluids with which the tissues in the 

 body are surrounded. 



These normal fluids are 



a. The aqueous humour of the eye. 



b. Blood-serum. 



If, then, a fresh tissue is to be observed from e.g. a 

 rabbit, the cornese should be punctured to obtain the 

 aqueous humour, or the blood should be allowed to 



