230 CLINICAL BACTERIOLOGY. 



sodium chlorid and albumin, can be preserved for an in- 

 definite time without any addition, and it is readily soluble 

 in water. One gram contains at least 5000 immunity-units, 

 and in some preparations as much as 10,000 immunity- 

 units. From -jig- to ^ gram thus represents a simple cura- 

 tive dose ; from ^ to % gram, twice as much, for severe 

 cases ; and from ^ to y 2 gram, four times as much, for 

 advanced cases. Behring considers it desirable that the 

 preparation of these solutions should be undertaken by 

 pharmacists, and he is hopeful that the dried serum may 

 in due time be incorporated into the Pharmacopeia. 



Prophylaxis. It is important to know that after com- 

 plete disappearance of the membrane virulent diphtheria- 

 bacilli may persist in the mouth and pharynx of children 

 until the fifth week, and sometimes even much longer. 

 The children must, therefore, be isolated for from five to six 

 weeks after recovery from the disease, and, above all, be 

 kept from school during that time. Those who surround 

 the patient should also be kept under medical observation. 

 Careful disinfection of the sick-room is a matter of impor- 

 tance, as it is known that diphtheria-bacilli will persist 

 for a long time and most tenaciously in a house in which 

 there has been a case of diphtheria. 



With regard to personal prophylaxis by means of injections 

 of antitoxin, this has not yet been employed upon a large 

 scale. An injection of 250 normal antitoxin-units confers 

 protection lasting three or four weeks. This will suffice in 

 most cases, but if the danger of infection continues for a 

 longer time, a second prophylactic injection will become 

 necessary. The main objection that has hitherto stood in 

 the way of this form of diphtheria-prophylaxis was the fear 

 of disagreeable complications due to the serum. Such fear 

 would, however, be removed by the use of a highly con- 

 centrated antitoxin in powder-form, as 0.025 gram of the 

 powder with a strength of 10,000 contain the requisite 250 

 immunity-units. 



TETANUS. 



The exciting agent of tetanus was recognized by 

 Nicolaier, of Gottingen, in 1885, as a bristle-like rod with a 

 terminal bulbous spore, but it was first isolated by Kitasato 

 in 1889 from the foreign bacteria always associated with it 



