THE TUBERCLE BACILLUS 591 



The medium used by Petroff is made as follows: 



I. Meat Juice. Five hundred grams of beef or veal are infused in 500 

 c.c. of a 15 per cent solution of glycerin in water, in a cool place. After 

 twenty-four hours the meat is squeezed in a sterile press and the infusion 

 collected in a sterile beaker. 



II. Eggs. The shells of the eggs are sterilized by ten minute immersion 

 in 70. per cent alcohol. They are broken into a sterile beaker, well mixed 

 and filtered through sterile gauze. One part of meat juice is added to two 

 parts of egg by volume. 



III. Gentian Violet. One per cent alcoholic solution of gentian violet 

 is added to make a final proportion of 1 :10,000. 



The three ingredients are well mixed. The medium is tubed and inspissated 

 as usual. 



Petroff recommends for sputum the following technique: Equal parts of 

 sputum and 3 per cent sodium hydroxid are shaken and incubated at 38 C. 

 for fifteen to thirty minutes, the time depending on the consistency of the 

 sputum. The mixture is neutralized to litmus with hydrochloric acid and 

 centrifugalized. The sediment is inoculated into the medium described above. 

 Pure cultures are obtained in a large proportion of cases. 



PetrofFs method has been applied by him to feces, in which the problem 

 is made more difficult by the presence of many spore-formers which resist 

 sodium hydroxid. Feces is collected and diluted with three volumes of water, 

 and then filtered through several thicknesses of gauze. The filtrate is saturated 

 with sodium chlorid and left for half an hour. The floating film of bacteria 

 is collected in a wide-mouthed bottle and an equal volume of normal sodium 

 hydroxid is added. This is shaken and left in the incubator for three hours, 

 shaking every half hour. It is then neutralized to litmus with normal 

 hydrochloric, centrifugalized, and the sediment planted. 



Once isolated, the bacilli are best grown on glycerin egg medium 

 which is described in the section on Media. On this medium colonies 

 of the human bacilli begin to appear after six or eight days as yellowish 

 white moist crust-like flakes. 



On blood serum at 37.5 C., colonies become visible at the end of eight 

 to fourteen days. They appear as small, dry, scaly spots with corru- 

 gated surfaces. After three or four weeks, these join, covering the sur- 

 face as a dry, whitish, wrinkled membrane. Coagulated dog serum is 

 regarded by Theobald Smith 18 as a favorable media for the growth of 

 tubercle bacilli. 



ls Tli. NM////J, .lour. Hxp. Mod., iii, 1898. 



