198 PRACTICAL HISTOLOGY. 



The bits, though small, will probably be large 

 enough to hold in the hand and cut without embed- 

 ding. Sections may be made both across and along 

 the course of the bronchial tubes, stained with log- 

 wood (it will be found that the sections must be left 

 for a considerable time in logwood, for they stain 

 with difficulty), and, after going through the usual 

 processes, mounted in dammer. 



Preparation 5. But, owing to its spongy nature, 

 it will be found almost impossible to cut very thin 

 sections unless the interstices of the tissue are filled 

 with some firm material, and the following directions 

 may accordingly be observed, if thinner sections than 

 can be obtained in the ordinary way are desired. A 

 small piece only (not larger than a kidney-bean) of 

 the lung hardened as above described is placed for 

 two days in alcoholic solution of logw r ood Kleinen- 

 berg's. 1 The piece of .tissue will have been stained 

 throughout of an intense dark violet color, and will 

 look almost black. On removal from the staining 

 fluid it is transferred through alcohol to oil of cloves. 

 After an hour in this, by which time the oil will 

 have had time to penetrate its whole thickness, it is 

 put into melted cacao-butter, which is kept in the 

 fluid condition by a temperature of not more than 

 42 C., and allowed to lie in this for four hours. 

 An oblong cake of the cacao-butter having been pre- 

 viously made by pouring some of the melted fat into 

 a paper mould, a little pit is scooped in it near one 

 end, and the piece of tissue, now soaked through 



1 Kleinenberg's solution is made in the following way (Foster 

 and Balfour) : 



(1) Make a saturated solution of crystallized calcium chloride 

 in 70 per cent, alcohol, and add alum to saturation. (2) Make 

 also a saturated solution of alum in 70 per cent, alcohol. Add 

 (1) to (2) in the proportion of 1 : 8. To the mixture add a few 

 drops of a saturated solution of haimatoxylin in absolute alcohol. 



This solution may be used in very many csiscs for staining sec- 

 tions, in place of the ordinary watery solution of logwood alum. 

 Jt may, if required, be diluted with the mixture of 1 and 2. The 

 stained sections are placed at once in strong spirit. 



