764 Syphilis 



prepared). Permit it to act for ten seconds. Tbe lead unites with^the, albumin 

 to form lead albuminate which is insoluble in water. 



4. Wash thoroughly in running water. _ , _ 



5. Cover the smear with a 10 per cent, aqueous solution of sodium sulphid. 

 This is. to act ten seconds, during which the salt transforms the lead albuminate 

 into lead sulphid and causes the preparation to turn brown. The qsmic acid 

 when reapplied causes it to become black. 



6. Wash thoroughly in running water. 



The whole process is to be repeated in exactly the same manner 

 three times, the washings all being very- thorough. The preparation 

 is then dried and mounted in Canada balsam. The micro-organisms 

 and cellular detritus are stained black. 



Fig. 303. — Treponema pallidum impregnated with silver. Film prepared from 

 the skin of a macerated, congenitally syphilitic fetus. X 750 diameters (Flex- 

 ner). The dense aggregation of organisms may indicate agglutination. 



When serum from a primary sore or other syphilitic lesion is; 

 treated by these methods, a number of the treponemas appear well 

 stained and a number very palely stained, so that one is in doubt 

 whether there may be many others unstained, and this seems to be 

 the case, for, when similar smears are treated by other methods many 

 more can be foimd. 



Stern* has appUed the method of silver incrustation to the ex- 

 amination of films by the following simple procedure: 



Spreads are made in the usual manner, dried in the air, and then for a few hours 

 in an incubating oven at 37°C. They are next placed in a 10 per cent, solution of 

 nitrate of silver in a colorless glass receptacle and allowed to rest in the diffused 

 daylight of a comfortably lighted room for a few hours, until they become brown- 



* "Berliner klin. Wochenschrift," 1907, No. 14. 



