460 PREPARATION, MOUNTING, AND COLLECTION OF OBJECT 



accomplished experts, with the most complete of the many almost 

 perfect recent microtomes, is one of the most refined and beautiful 

 with which the scientific mind can concern itself. The combined 

 cutting, staining, and mounting of the most delicate organic tissues in 

 almost every conceivable state has thrown a light upon histological 

 and pathological matters, the present and prospective value of which 

 we can scarcely estimate too highly ; while some of the profoundest 

 and most interesting questions of biology are opening themselves to 

 renewed research by its means. 



Throughout this chapter we only seek to give the possessor of a 

 good microscope a fair outline of the principal methods employed, 

 and clues to the finest processes in detail, for histological, patholo- 

 gical, and embryological work. For full details we may refer him 

 to the more or less exhaustive handbooks which the several subjects 

 have called forth, the fullest account of the subject' being that given 

 in Mr. A. Bolles Lee's ' The Microtomist's Yade-Mecum.' But we 

 are at the same time convinced that if the student be but rightly 

 directed as to instruments and the best way of employing them, and 

 at the same time have the best general processes concisely indicated 

 to him, he will soon discover what to him will be the most facile and 

 satisfactory method of obtaining the best results. In the hands of 

 an original worker prescriptions are only satisfactory starting-points 

 to better methods. We shall therefore describe one microtome 

 which we believe, on the whole, to be the best, and sufficiently 

 indicate the character and peculiarities of two or three others, to 

 enable the student, as we believe, to judge for himself in considera- 

 tion of his future purpose as to which will best serve him in the 

 object he has in view. 



It will be as well, however, to note that extremely thin sections 

 are not the supreme purpose of microtomes. Good sections, treated 

 with success from beginning to end, are the first consideration. The 

 tenuity of a section must be proportional to the character of the 

 tissue. 



Manifestly a tissue with injected arteries or veins must be thick 

 enough to contain some of these vessels with their branches entire. 

 If we require to study the hepatic cells or the renal tubules we must 

 give depth enough in the sections to include these. But it will be 

 found that the hardening and imbedding agents contract greatly, 

 without distorting, the anatomical elements, and sections much 

 thinner than would be normally required to completely disclose what 

 is sought may be often successfully made in tissues so prepared. 



It is none the less true that a mere race for extreme attenuation 

 in sections is in every sense undesirable ; and for extremely thin 

 sections say the -^L^th of an inch in thickness, or less only small 

 sections should be attempted. 



Here it may be advisable to state that the standard unit in 

 microscopy, as accepted by the Council of the Royal Microscopical 

 Society, 1 is the -j^^th of a millimetre, which is indicated by the 

 sign /;, being known as a micron. 



1 Jowrn. Boy. Micro. Soc. ser. ii. vol. vii. pp. 502, 526 ; Nat. xxxviii. p. 221. 



