THE PRESERVATION OF SPECIMENS. 313 



The blocks should be made so that the grain of the wood ex- 

 tends along the longer dimension of the block, i. e., from top to 

 bottom in the first two sizes, and from left to right in all others. 



Bent-necked Vials. — It is necessary to preserve many speci- 

 mens in alcohol, and it is very desirable that such specimens should 

 be mounted on blocks so as to be placed with other specimens illus- 

 trating the same species. The use of the ordinary vials or glass 

 tubes for this is attended with serious difficulties. It is almost im- 

 possible to prevent the leakage of the alcohol and the consequent 

 destruction of the Gpecimens. In addition 

 to this the curved surface of a vial will make 

 the contained specimen appear very different 

 from what it is. A long slender larva will 

 appear much thicker than it is, while its 

 length will not be magnified. '''°;«?er^a?.'°*' 



To meet these difficulties the v/riter has 

 had vials made of the form represented in Fig. 279. The bend in 

 the neck prevents the rapid leakage of alcohol, and the plain sides 

 the magnification of one diameter of the contained specimens. Two 

 sizes of these vials are manufactured — one containing one half 

 ounce, the other two ounces. They can be obtained of Messrs. 

 Whitall, Tatum & Co., New York. 



To fix one of these vials to a block a white card is fastened to 

 its lower side with liquid glue (the acetic acid and alcohol solution). 



Fig. 280. — Clips for slides on a block. Fig. 281. 



The card is then trimmed close to the sides of the vial, but is al- 

 lowed to project a short distance beyond each end ; then the card is 

 fastened at each end to the block with ribbon pins. 



on the inside fifteen inches by eighteen inches. This would admit of 

 four columns of blocks, each block being four inches and a half long ; 

 but in order that the blocks may be easily removed from the case they 

 are made a little shorter than this. 



