490 BACTERIOLOGY. 



a dose of 1.5 c.c. introduced subcutaneously or intraperi- 

 toneally (Selander). In the latter case, Metchnikoff has 

 shown that the serum of the immunized animal has neither 

 antitoxic, germicidal nor attenuating- action. It will not 

 protect against the soluble toxin! The serum, therefore, 

 is anti-infectious and stimulates the phagocytes to destroy 

 the bacterial cells. 



Eisner's Medium. 



Eisner's medium ] is a potato gelatin to which 1 per 

 cent, of KI has been added. It is prepared according to 

 the method of Holz. 2 The details of preparation as given 

 by these authors are 1 very meager and unsatisfactory. The 

 method of preparation as adhered to in this laboratory fol- 

 lows as closely as possible the original data. 



1,000 g. of potatoes are weighed out. The potatoes are 

 brushed clean under the tap and cut up into lumps which 

 are then placed in an Enterprise fruit-press (No. 34). The 

 potato comes through in a finely mashed condition. A 

 sausage machine is not as useful since it cuts up the potato 

 into small lumps, and when in this condition less juice can 

 be obtained on subsequent squeezing. The finely mashed 

 potatoes are placed in muslin and squeezed as much as pos- 

 sible. The dark colored juice is saved. The potato mass, 

 wrapped in muslin, is then placed in a press and pressure 

 applied. The liquid thus obtained is combined with the 

 former. About 400 c.c. of a dark liquid is thus expressed 

 out of 1 kg. of potatoes. 



The liquid is set aside in the ice-chest for 24 hours, 

 after which it should be filtered. Owing to the presence of 

 extremely small granules, the liquid can not be readily 

 filtered through paper. It is advisable, therefore, to filter 



1 Zeitschrift fur Hygiene 21, p. 29, 1896. 



2 Ibid, 8, p. 159, 1890. 



