H4 PA THOGENIC BA CTERIA . 



the temperature elevated until coagulation occurs. The 

 repeated sterilizations may be conducted in this apparatus, 

 or may be done equally well in the steam apparatus, the 

 cover of which is not completely closed, for if the tem- 

 perature of the serum is raised too high it is certain to 

 bubble. 



Loffler's blood-serum mixture, which seems rather 

 better for the cultivation of some species than the blood- 

 serum itself, consists of i part of a beef-infusion bouillon 

 containing i per cent, of glucose and 3 parts of liquid 

 blood-serum. After being well mixed this is distributed 

 in tubes, and sterilized and coagulated like the blood- 

 serum itself. Most organisms grow more luxuriantly 

 upon it than upon either plain blood-serum or other 

 culture-media. Its special usefulness is for the Bacillus 

 diphtheriae, which grows upon it with rapidity and with 

 quite a characteristic appearance. 



Potatoes. Without taking time to review the old 

 method of boiling potatoes, opening them with sterile 

 knives, and protecting them in the moist chamber, or 

 the much more easily conducted method of Ksmarch in 

 which the slices of potato are sterilized in the small 

 dishes in which they are afterward kept and used, we 

 will at once pass to what seems the most simple and 

 satisfactory method of using this valuable medium that 

 of Bolton and Globig : 



With the aid of a cork-borer a little smaller in diam- 

 eter than the test-tube ordinarily used a number of cyl- 

 inders are cut from potatoes. Rather large potatoes 

 should be used, the cylinders being cut transversely, so 

 that a number, each about an inch and a half in length, 

 can be cut from one potato. The skin is removed from 

 the cylinders by cutting off the ends, after which each 

 cylinder is cut in two by an oblique incision, so as to 

 leave a broad, flat surface. The half-cylinders are placed 

 each in a test-tube previously sterilized, and then are 

 exposed three times, for half an hour each, to the pass- 

 ing steam of the sterilizer. This steaming cooks the 



