[ 41] 



Zbc flDicro6cope an^ bow to use it 



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



Part VIII. — Injecting. 



THE term injecting, in its micrological application signifies 

 the filling of the arteries, veins, and other vessels of animals 

 with coloured substances, for the purpose of showing their 

 arrangement in relation to, and their course through, the tissues. 

 Practice, patience, and perseverance are required to make good 

 injections ; still more does the remark apply to injecting morbid 

 tissues, which have been excised out of the living body, as in this 

 case there are so many vessels, which have been severed, requiring 

 to be ligatured to prevent the escape of the injection. In cases of 

 morbid tissues it is best to use co/d injections^ as heating often 

 causes considerable alterations in the tissues, especially where 

 there is much epithelium, which has already become somewhat 

 changed during the period that has elapsed since death. Injec- 

 tions may be either opaque or transparent, each method having its 

 special advantages. The former is most suitable where solid form 

 and inequalities of surface are especially to be displayed ; the latter 

 is preferable where the injected substance is so thin as to be 

 transparent (as in the case of the retina, etc.), or where the distri- 

 bution of its blood vessels and their relation to other parts may be 

 displayed by sections thin enough to be made transparent by 

 mounting in such medias as Balsam and Dammar. 



Let me beg of the amateur to note carefully the causes of each 

 failure, and to take precautions to avoid these in his subsequent 

 practice. If this is done, the art of injecting will be learned 

 sooner and more easily than it otherwise could be. There are 

 three well-known methods of making injections, which are as 

 follows : — 



(i) Injections made with a syringe. 



(2) Mechanical injections, in which the function of the 

 syringe is replaced by the pressure of a column of water, or 

 mercury. 



