BONE, TEETH 429 



two changes of pure carbon disulphide, each of fifteen minutes, 

 then for thirty minutes into carbon disulphide saturated with 

 paraffin at 30° C, transferred to carbon disulphide saturated with 

 paraffin at 42° C. for a like period, and finally into two baths 

 of paraffin, in each half an hour. Imbed for cutting in pure 

 paraffin. 



By the employment of this method the amount of shrinkage 

 in the tissues is extremely slight and the dentine does not become 

 hardened, so that the tooth-germs of the incisors may be cut without 

 decalcification. In the case of the canine and molar tooth-germs 

 a short period of decalcification may be necessary, and for this 

 purpose a rapid and delicate method lies in the employment of 

 Zeigler's method (Festschr. f. Ktipffer, 1899, p. 51), in which, 

 by the use of a 5 per cent, solution of sulphurous acid, the insoluble 

 tricalcium phosphate is changed into the readily soluble mono- 

 calcium phosphate. 



To demonstrate cytological detail no stain equals iron haema- 

 toxylin followed by a counterstain of picric-lichtgrun or of 

 Rubin S in picrate of ammonia. 



It cannot be too strongly emphasised that the precision of staining 

 methods depends on the rapidity with which fixation of the tissues 

 is effected after death. 



For large jaws imbedding in celloidin, or, when serial sections 

 are required, double imbedding in celloidin, parlodion or photo- 

 xylin and paraffin is recommended (§ 181). 



Mummery {Phil. Trans. B., ccviii, 1917, p. 258) deprecates 

 the employment of paraffin for imbedding the tooth-germs of 

 fishes, considering the heat employed to be very injurious to the 

 delicate enamel organs, and advocates the use of the freezing 

 method in obtaining sections. See carbon disulphide method 

 above. 



Nealey (Amer. Man. Mic. Journ., 1884, p. 142 ; Joiirn. Roy. Mic. 

 Sac, 1885, p. 348) says that perfectly fresh portions of bone or teeth 

 may be ground with emery on a dentist's lathe, and good sections, with 

 the soft parts in situ, obtained in half an hour. 



Hopewell-Smith (Journ. Brit. Dent. Ass., xi, 1890, p. 310 ; Journ. 

 Roy. Mic. Soc, 1890, p. 529) says that for preparing sections of teeth 

 showing odontoblasts in situ the best plan is to take embryonic tissues. 

 A lower jaw of an embryonic kitten or pup may be taken, and hardened 

 in solution of Miiller followed by alcohol, then cut with freezing micro- 

 tome. 



Weil (Zeit. Mikr., 1888) fixes pieces of fresh teeth in sublimate, stains 

 with borax carmine, brings them through alcohol into chloroform and 

 chloroform balsam, and after hardening this by heat proceeds to grind 

 as usual (§ 910). 



916. For the study of the vessels in teeth, Lepkowsky {Anat. 

 Hefte, viii, 1897, p. 568) injects with Berlin blue, hardens the 

 teeth with a piece of the jaw for one or two days in 50 per cent. 



