380 INFECTION AND IMMUNITY. 



blood and bacterial suspension and then diluting 

 and smearing on a slide. The dilution should be 

 about five times. The method of measuring equal 

 small volumes by means of capillary tubes as 

 given in Chapter XIX, may be used and a 

 Bomanowski stain used for staining. 



Since the number of corpuscles in normal 

 human blood is about 5,000,000, by a comparison 

 of the number of bacteria with the number of 

 corpuscles the number of bacteria per cubic cen- 

 timeter can be readily estimated. By dilution with 

 salt solution the required dosage per cubic cen- 

 timeter may be obtained. When it is necessary to 

 keep the vaccine a small amount of tri-cresol (.2 

 per cent.) may be added. 



Recently therapeutic inoculations have been used 

 for a great variety of infections, both acute and 

 chronic, and to both local and systemic infections. 

 Naturally, the results have also varied within wide 

 range. 



In case of chronic localized infections the 

 theoretical basis for the use of vaccines seems 

 plain. As pointed out by Theobald Smith: "The 

 effectiveness of vaccines applied in the course of 

 acute febrile diseases, such as typhoid fever and 

 pneumonia must be accounted for by principles of 

 which experimental medicine has as yet no definite 

 knowledge." Theoretically no advantage can be 

 expected from adding toxins in an already over- 

 intoxicated case. 



This criticism does not apply, of course, to such 

 a procedure as is suggested by Eosenow. (See chap- 

 ter on Pneumonia.) 



