The Microscope. 303 



heat just the point of boiling. Examination 'will show large 

 numbers of perfect crystals, which should be sought for in the more 

 open spaces. In case of doubtful stains, this test is valuable to 

 determine whether blood be present or not. If sufficient of the. 

 stain can be washed on to the slide to make a dark yellowish mixture 

 with water, the test can be applied. Do not forget to dry the 

 specimen before the test is applied as the presence of water inter- 

 feres with the test. 



Permanent Preparations of Blood. — Beautiful specimens of 

 blood can be prepared by properly staining and mounting. 

 Amphibian blood is to be preferred, as the red cells are so large and 

 contain such prominent nuclei. A large number of stains have been 

 proposed, many of them being most excellent. Numerous tests of 

 the various stains were made in the laboratory of this journal, and 

 one called the Heidelberg method (originator's name not known) was 

 found to be the most satisfactory. It is as follows : 



Allow fresh blood to fall drop by drop into a solution of osmic acid 

 (2 per cent, acid solution, one part ; 1 per cent, solution sodium chlo- 

 ride, two parts ; distilled water, one part.) The solution should be 

 constantly stirred while the blood is dropping. Allow the blood and 

 acid to stand over night, and then wash the acid away with distilled 

 water. Add alcohol, then clove oil, in which the blood may be kept 

 indefinitely. Before the alcohol is added, the nucleus of the 

 corpuscle may be stained in alum- carmine, the blood afterwards 

 being washed ; or the whole corpuscle may be stained in analine 

 blue. The alum-carmine is to be preferred, as being more perma- 

 nent. Mount in balsam. We have slides of salamander and dog's 

 blood prepared in this way some years ago, which are as beautiful 

 to-day as when first finished. 



EUDIMENTS OF ^K ACTIO AL EMBRYOLOGY.* 



W. p. MANTON. 

 THE PAPER CELL. 



§ 10. This may be made of stiff glazed paper, card-board or 

 canceled postal card, and of any size. A convenient shape for a 

 small embryo is one and a half inches long by three-fourths wide 

 and half an inch deep. Having cut the card of the required size, 

 begin by folding down each side of a width to give the cell the 



♦Copyrighted 1888. 



