PRACTICAL DIRECTIONS. [API*. 



we are indebted to Dr Kleinenberg, is made in the 

 following way. 



1. Make a saturated solution of crystallized calcium 

 chloride in 70 p. c. alcohol, and add alum to 

 saturation. 



2. Make also a saturated solution of alum in 70 p. c. 

 alcohol, and add 1 to 2 in the proportion of 1:8. 



3. To the mixture of 1 and 2 add a few drops of a 

 'barely alkaline saturated solution of hsematoxy- 

 lin. 



The embryo may be removed into this directly 

 from the absolute alcohol, left in it for 5 hours 

 and placed back again in absolute alcohol for 24 

 hours. 



Neither the carmine nor the haematoxylin will 

 stain if the embryo is not quite free from acid. 



Only the chromic or picric acid specimens re- 

 quire to be stained. It is however possible to stain 

 the osmic acid specimens with hsematoxylin. 



3. IMBEDDING. 



It is hardly possible to obtain satisfactory sec- 

 tions of embryos, without employing the method of 

 imbedding now so largely employed in histological 

 studies. 



The substances most generally used, are: 



1. Paraffin, obtained by heating together five parts 

 of solid paraffin with one part of paraffin oil and 

 one part of pig's lard. 



2. Wax and oil, made by heating together three parts 

 of common white wax and one of olive-oil. 



3. Spermaceti, obtained by heating together very 

 thoroughly four parts of spermaceti and one of 

 cocoa butter, or four parts of spermaceti and one 

 of castor oil. 



[4. Gum. The above substances are all liquid when 

 warm, and become solid when cold. When a 

 solution of gum is used as an imbedding medium, 



