LARYNX AND TRACHEA. 201 



injection has been set flowing through the pulmo- 

 nary vessels the lungs are pretty fully distended 

 with the cacao-butter; the pressure is then raised 

 in the injecting apparatus to about four inches of 

 mercury. The left ventricle is first slit, to let the 

 blood out of the pulmonary system, and then 

 clamped, to prevent the escape of the injecting fluid, 

 which is allowed to pass in for a few minutes until 

 it is thought that the vessels must all be completely 

 filled ; this can be partly made out from the color 

 which the lungs assume. The trachea and the base 

 of the heart are then ligatured, and the whole is left 

 for some time to cool, so that both gelatine and 

 cacao-butter are fully set. The lungs are then cut 

 out and placed in weak spirit ; after a day they are 

 transferred to strong spirit, and in another clay or 

 two sections may be made (mostly vertically to the 

 surface of the lung), placed in warm oil of cloves, to 

 dissolve out the cacao-butter, and then mounted in 

 dammar. If it is desired to stain the tissue some- 

 what, so as to show the general structure of the lung 

 as well as the arrangement of the bloodvessels in 

 the same preparation, this can be done by placing 

 the sections, after the cacao-butter has been dissolved 

 out of them, first in absolute alcohol, to get rid of 

 the oil of cloves, and then for a few minutes in 

 Kleinenberg's logwood until they are sufticiently 

 colored. The transference through absolute alcohol 

 and oil of cloves into dammar is then proceeded 

 with, as in the case of other sections. 



Preparation 8. Larynx and trachea. The 

 trachea and larynx are hardened in per cent, 

 chromic acid (ten days), the hardening being com- 

 pleted by spirit, and the sections, which may be 

 longitudinal of the cartilaginous part and transverse 

 of the posterior membranous part, are to be stained 

 with logwood (they will require a considerable time), 

 and mounted in dammar. It will, of course, be 

 necessary to embed the tissue, and it will be found 

 advantageous in cutting to pass from the mucous 



