248 APPLIED BACTERIOLOGY 



maintaining the cultivations at a constant virulence. By 

 using a special method of cultivation, it was found possible 

 to preserve the virulence of the pneumococcus at an abso- 

 lutely constant level for a long period. The medium em- 

 ployed consisted of agar streaked with sterile rabbit's blood. 

 The minimal fatal dose of Dr. Washbourn's pneumococcus for 

 rabbits and mice was O'OOOOOl loop of the cultivation. (The 

 loop held about 0*5 mg.) Plate cultivations showed that this 

 quantity contained about 200 living cocci. For the purpose 

 of standardization, the serum, in varying quantities, was 

 mixed with a tenfold fatal dose of the cultivation, and the 

 mixture was injected into the peritoneal cavities of rabbits, 

 control experiments with the minimal fatal dose always 

 being made. The smallest quantity of serum which will 

 protect the animals under these conditions is called a unit. 

 The most powerful serum Dr. Washbourn has yet obtained 

 from the pony was of such a strength that 0"03 c.cm. pro- 

 tected against the tenfold fatal dose. A cubic centimetre 

 of this serum, therefore, contained 33 units. 



As far as the therapeutic value of the serum is concerned, 

 Dr. Washbourn's experiments show that 2 com. of the 

 serum will protect when injected during the first quarter of 

 the disease — that is to say, within the first six hours in the 

 case of rabbits. The same dose does not protect when 

 injected at a later period. In applying this method of 

 treatment to cases of pneumonia in the human subject, it 

 follows that the earlier the treatment is commenced the 

 greater the chance of success. As far as the dose is con- 

 cerned. Dr. Washbourn states that at least 600 units 

 should be injected twice a day. 



Furthermore, Dr. Washbourn states that from the nature 

 of the serum, no immediate beneficial effect is likely to be 

 observed after injection. It is only after treating a large 

 number of cases that a definite conclusion can be arrived 



