[ 231 J 



ITbe flDicroacope anb Ibow to W< it 



By V. A. Latham, F.M.S. 

 Part IV. — Practical Histology. 



THE study of Histology is attended with more difficulty than 

 that of Botany or Geology, and owing to the study being 

 also an extensive one we can only give the simplest 

 details. Nearly all the methods recommended have been tried 

 with success, and are mostly gathered from British and foreign 

 text-books, special prominence being given to the later methods 

 of staining. 



Tissues. — It is of the utmost importance that the tissues 

 should be fresh, and the animals most suitable are cat, dog, rat, 

 guinea-pig, and frog. As some fluids alter the normal appearance 

 of the tissues, they should, in the first instance, be examined in 

 their 07C'n fluid. It should be carefully borne in mind that the 

 specific gravity of whatever fluid is employed must be the same 

 as that of the tissue under examination ; also that the solubility 

 or non-solubility of the tissue in the particular fluid-medium 

 employed must be carefully taken into consideration, as the fol- 

 lowing facts will shovv' : — Earthy salts are soluble in chromic and 

 nitric acids, oils in ether, albuminous matters in acetic acid, the 

 object of adding a fluid being to regulate the degree of trans- 

 parency of the tissue, according as its examination is facilitated 

 by the augmentation or diminution of the same. The chemical 

 relation between the tissue and the fluid-medium employed must 

 necessarily be considered. The normal fluids most commonly 

 used are lymph, serum, amniotic and pericardial fluid, iodised 

 serum or dilute albumen. The methods of preparation will be 

 given in a future part. 



Single Staining.— The best and most useful stains are log- 

 wood, picro-carmine, Bismarck brown, carmine, and aniline blue, 

 but numerous others will be given, so that students may try them 

 and choose their own stains. Staining may be either single, 

 double, or treble in its application. 



\X>L. IV. ' R 



