OF MICROSCOPIC OBJECTS. 167 



slide, and before it becomes dry pour over it two or three 

 irops of pyroacetic acid for about half a minute. Tilt this 

 off and replace by chloroform. Watch the effects, as before, 

 under the microscope, and then cover with the Canada 

 I'alsam solution and finish. These specimens, however, are 

 not always permanent in their appearance, according to the 

 results of some. 



Mr. Alfred Banders gives his experience as differing some- 

 what from this. He says The brain, or other structure, 

 being, as usual, hardened in chromic acid, the section is put 

 for a short time in spirits of wine, and thence transferred to 

 the creosote, which makes it transparent in a few minutes, 

 when it is placed in Canada balsam. The balsam will mix 

 easily with the creosote, or the solution in benzole may be 

 employed. 



TEACHER or INSECTS, &c. The nature of these was de- 

 scribed in Chapter IV., but the method of procuring them 

 was not explained., as this clearly belongs to dissection. 

 The larger tubes are readily separated by placing the insect 

 in water, and fixing as firmly as possible, when the body 

 must be opened and the viscera removed. The trachess may 

 then be cleaned by the aid of a carael-hair pencil, and 

 floated upon a glass, where they must first be allowed to dry, 

 and then be mounted in balsam. Mr. Quekett gives the 

 following method of removing the tracheae from the larva of 

 an insect : " Make a small opening in its body, and then 

 place it in strong acetic acid. This will soften or decompose 

 all the viscera, and the tracheae may then be well washed 

 with the syringe, and removed from the body with the 

 greatest facility, by cutting away the connections of tho 

 main tubes with the spiracles by means of fine-pointed 

 scissors. In order to get them upon the slide, it must bo 

 put into the fluid, and the tracheae floated upon it; after 

 which they may be laid out in their proper position, then 

 dried and mounted in balsam." If we wish them to bear 

 their natural appearance, they must be mounted in a cell 

 with Goadby's fluid; but the structure is sometimes well 



