BeOOK : SUMMAEY OF METHODS OF MICROSCOPICAL RESEARCH. 35 



Methods of Injection. — Prof. Emery, who has lately studied the 

 methods of injection, recommends the following : — (A) For injection 

 of thick carmine he follows the prescription of Ranyier, in his " Trail e 

 d'histologie techinque," but neutralises the mass in a more simple 

 way. Acetic acid is added by drops until the smell of ammonia 

 becomes very faint. The reaction of the vapour is then tried with 

 litmus paper. Sufficient acid has been added when the litmus paper 

 begins to get red. Often, on stirring, the alkaline reaction will 

 return, but this must be removed by another drop of acetic acid. In 

 use it will be found that with a neutral or slightly acid mass, a 

 diifusion of the medium through the cell walls is scarcely likely to 

 occur. (B.) As a cold fluid mass, Emery recommends the carmine 

 solution prepared with 10 % ammonia, to which, while continually 

 stirring, acetic acid is added until the carmine begins to be precipi- 

 tated, and the liquid has a blood-red colour. The clear liquid only 

 must be used, and after injection, the objects mast be at once placed 

 in strong alcohol, to fix the carmine. (C.) For injecting the capil- 

 laries, good results are often obtained by gradually mixing 10% 

 carmine solution with acetic acid, until part of the carmine is precipi- 

 tated. The solution must be shaken shortly before use, only allowing 

 it to settle for a few minutes, so that the coarser grains do not get 

 into the syringe. In injections from the arteries a considerable 

 quantity of fine sediment remains in the capillaries, while only a light 

 fluid enters the veins. Thus the veins can easily be distinguished 

 from the arteries, which are dyed dark red. 



Mounting Methods. — The great object aimed at, in preparing per- 

 manent preparations for the microscope, is to entirely get rid of the 

 water in the tissues of the object, and supplant it by a preservative 

 medium. Hence, at Naples the aqueous mounting media such as 

 glycerine, glycerine jelly, acetate of potash, &c., are in little favour. 

 After the water has been forced from an object and supplanted by 

 alcohol, the process is usually completed by passing through oil of 

 cloves and mounting in balsam. Usually there is little trouble with 

 this method. The oil of cloves, or other similar oil, is slightly 

 heated, and as a rule it will penetrate the tissues without trouble. 

 With larger objects, however, and particularly those with thin but 

 not easily permeable walls, the alcohol will often leave before the oil 

 can enter, and there will be a collapse of the walls. Creosote has 

 been used to prevent this shrinking, but it appears to render no 

 permanent good. 



(To he continued.) 



