236 THE MICROSCOPE. 



preserved perfectly in Mr. Goadby's No. 2 fluid, specific 

 gravity 1*100; tlie No. 1 fluid destroys them. 



" I would recommend that the slips of glass employed 

 for the dry preparation be instantly inscribed with the 

 name of the preparation, written with a diamond ; for, 

 when dry, it is difficult to recognise one preparation from 

 the other, until the operator's eye be educated to the 

 effects of this chemico-gelatinous injection. Where so 

 much wet abounds, gummed paper is apt to come off. 

 When dry, it is sufficient, for the purpose of brief exami- 

 nation by the microscope, to wet the surface of a prepara- 

 tion with clean oil of turpentine ; immediately after 

 examination, it should be put away carefully in a box, to 

 keep it from the dust, until it can be mounted in Canada 

 balsam. 



"The bichromate of potash is greatly superior in colour 

 to the chromate, which yields too pale a yellow; and sub- 

 sequent experience has proved that the acetate of potash 

 frequently effects its liberation by destruction of the 

 capillaries, and this even long after the preparations have 

 been mounted in Canada balsam; perhaps this may be 

 owing to some chemical action of the acetate of potash 

 upon them. I would suggest the substitution of the 

 nitrate for the acetate of lead, as we should then have, in 

 the liberated nitrate of potash, a valuable auxiliary in the 

 process of preservation. Although highly desirable, as 

 the demonstrator of the capillaries of normal tissues, I do 

 not think this kind of injection fitted for morbid prepara- 

 tions ; the infiltrated gelatine producing appearances of a 

 puzzling kind, and calculated to mislead the pathologist. 

 In preparing portions of dried well-injected skin for 

 examination by the microscope, I have tried the effect of 

 dilute nitric acid as a corroder with very good results. 

 But, probably, liquor potassa would have answered this 

 purpose better. 



"When size-injection is to be employed, coloured either 

 with vermilion or the chromate of lead, the animal should 

 be previously prepared by bleeding, to empty the vessels ; 

 for if they be filled with coagulated blood, it is quite im- 

 possible to transmit even size, to say nothing of the colour- 

 ing matter. Hence the difficulty of procuring good 



