230 



THE AMERICAN MONTHLY 



[December, 



damaged and fragmentary objects. 

 In fact, we will not cut off the tongue 

 at all, but mount it in its natural po- 

 sition on the head ; for our blow-fly's 

 neck is so slender that there is no 

 difificulty whatever in decapitating 

 him. We will, therefore, do so. Now, 

 if we consult our books on micro- 

 scopical mounting, we find that we 

 must first dry the head, and then 

 soak it in turpentine; or, as some say, 

 put it at once in turpentine and wait 

 till it is transparent. If mounting 

 anything but horses had been in vo- 

 gue in Methuselah's days, such me- 

 thods would have been then well 

 worth trying ; there was no need for 

 hurry in those happy times. Those, 

 perhaps, were the days when they 

 piaced knobs of " Wallsend " in car- 

 bonate of potash solution, and fished 

 them out a century or so later, just 

 nice and soft for cutting coal sec- 

 tions. Alas ! this is now a lost art, in 

 spite of the plain directions given in 

 various works on microscopical 

 mounting ! But as we cannot wait the 

 months necessary for the blow-fly's 

 head to become transparent (if it ever 

 would by this pfocess), we will try a 

 shorter plan ; for even in micro- 

 scopical mounting it is of some ad- 

 vantage to be reasonable. And in 

 order to make it transparent, we have 

 first to get rid of the mass of color- 

 ing matter and of all air; since, of all 

 things, air diffused through an object 

 is the most /^-transparent, — difficult 

 to get rid of, and misleading in its 

 appearances to the microscopist. 

 Most bodies contain about seventy 

 per cent, of water, and in drying an 

 object, therefore, we get rid of all 

 this, partly by shrivelling up the ob- 

 ject, partly by replacing the water 

 with air. Then, having spent some 

 time and effort to get the object well 

 filled with air and nicely shrunken 

 up, we set to work with still greater 

 trouble to get the air out again, and 

 to puff out the specimen to something 

 like its former shape. Hence, what- 

 ever else we do, we will not dry our 

 object. That part of the tissue of 



the blow-fly's head which is not swol- 

 len with water is filled with air; and 

 so, while taking out the coloring 

 matter, it will be an economy of time 

 to get rid also of some of the air. 

 What apparatus do we need for this ? 

 would not an air-pump be of use ? 

 By all means, if you can afford it, 

 and if you wish to add another to 

 your array of instruments go and 

 purchase an air-pump, and do what- 

 ever you like with it, only do not use 

 it for microscopical mounting. Go, 

 instead, and buy a half-penny test- 

 tube ; for a solitary test-tube is the 

 whole of the preparing apparatus 

 needed in this method ! 



Into this test-tube place the fly's 

 head, and fill the tube half-full with a 

 solution of soda or potash. Stand 

 the tube in a cup or tin pot of boil- 

 ing water, and leave it on the hob of 

 a fire or other warm place to keep hot 

 till morning. Then examine the head 

 and see if it looks almost transparent; 

 if not, pour off the soda-solution, and 

 add a fresh supply, and again keep 

 the tube hot till the object becomes 

 semi-transparent. Now pour off the 

 solution and add hot water, in a few 

 minutes emptying it out and adding 

 some more ; repeat this at least three 

 times, and finally leave the last quan- 

 tity of water on the object for an 

 hour to cool. Next pour off all the 

 water and replace it with spirit of 

 wine; methylated spirit, if strong, will 

 do sufficiently well. Heat this by 

 immersing the tube in a vessel of hot 

 water for one minute ; then take it 

 out, cork it up, and leave it for one 

 hour. 



So far, we have, by means of the 

 soda-solution, destroyed all the flesh 

 and fat-tissues, leaving only the cu- 

 ticle and internal organs, such as the 

 tracheae, etc. In doing this, we have 

 filled up most of the few natural air- 

 spaces with soda-solution; which, 

 'however, being a somewhat dense 

 fluid, would not enter many of the 

 narrow tracheal tubes. Then with 

 water we replaced the soda-solution, 

 and washed away the parts destroyed 



