284 THE PRINCIPLES OF IMMUNOLOGY 



its minimum period of incubation. The material is introduced into the 

 anesthetized rabbit by subdural inoculation. The injection is made 

 through a small trephine opening just back of the eye and to one side 

 of the median line. The injected material is ground with a small 

 quantity of I per cent, phenol solution and 0.2 c.c. of this emulsion is 

 injected. After the rabbit is completely paralyzed it is killed with 

 chloroform and the spinal cord removed aseptically. A small ligature 

 is placed around one end of the cord and the cord hung in a sterile 

 bottle in the bottom of which has been placed sticks of potassium 

 hydrate. The bottle is placed in an incubator maintained at 22 to 23 C. 

 Pieces I. cm. in length are cut off at daily intervals and placed in glycerol 

 where the degree of virulence on that particular day is retained for 

 several weeks. In large laboratories animals may be killed on suc- 

 cessive days and the whole cord employed in preparing the material 

 for human protection. In the United States Hygienic Laboratory 

 pieces 0.5 cm. in length emulsified with 2.5 c.c. of salt solution serve 

 for one injection. 



Inoculation in Man. The determination as to who shall receive 

 anti-rabic treatment is often difficult, but skilled veterinarians are 

 able to diagnose rabies in dogs almost invariably. Knowledge of the 

 condition of the animal inflicting a bite is of the utmost importance. 

 Although cats and rats are not uncommonly victims of rabies, this is 

 not frequently a source of infection in man. When a dog bite is re- 

 ceived, the animal should be captured and observed for at least two 

 weeks, during which time the symptoms of rabies become manifest. 

 If the animal is killed the brain should be sent in glycerol to the nearest 

 laboratory, where it may be examined for Negri bodies. If these are 

 not found, material should be injected into rabbits. Negative findings 

 in regard to Negri bodies in the dog's brain are not to be accepted as 

 evidence. In our opinion it is wise to administer treatment to all 

 individuals who have been bitten by animals showing any signs of 

 rabies. The material may be supplied to the physician either in the 

 form of small pieces of cord to be emulsified in salt solution or in the 

 form of an emulsion for dilution with salt solution. The injections 

 are given subcutaneously under the skin of the abdomen. If a con- 

 siderable time has elapsed since the bite or if the bite has been inflicted 

 upon the head or neck the so-called intensive method of treatment is 

 adopted. Under other circumstances the mild treatment may be given. 

 When material is requested from a commercial laboratory or a state 

 laboratory it is necessary to indicate which form of treatment is desired. 

 As an example of the two methods, the scheme of treatment as shown on 

 page 285, adopted by the New York City Board of Health, will serve. 



The Effects of Treatment. Local reactions are frequent and are 

 likely to be severe about the eleventh and nineteenth days of inocula- 

 tion. These are urticarial in character and the more severe reactions 

 may be accompanied by mild constitutional symptoms. The glycerol 

 contained in the emulsions not infrequently produces severe pain for 



