504 BACTEEIOLOGY. 



bottle marked B. In like manner the upper third of the cord is tied 

 with a silk thread, the connections cut loose, and lastly the cord is 

 severed below the pons. This section of the cord is suspended in a 

 bottle marked A. 



The bottles containing the cords are set aside at a constant tem- 

 perature of about 23°. The cords thus undergo desiccation, and, as a 

 result, the virus gradually loses its virulence and becomes attenuated. 

 From day to day, a portion of each cord is cut ofi and planted in bouil- 

 lon. If bacteria develop it must be discarded. Suspensions in steril- 

 ized water or bouillon of the desiccated cords are employed in the pre- 

 ventive inoculations against rabies. 



The brain and medulla are removed and placed in a sterile dish. 

 A portion of the medulla about the size of a grain of wheat is placed 

 in a sterilized test-glass (Fig. 43). By means of a sterile drawn-out 

 tube pipette, a few drops of sterile water are added from time to time, 

 and the tissue is reduced to a pulp by means of a sterile glass rod. 

 When the insoluble matter has settled, the cloudy suspension, 

 amounting to about 3 c.c. is drawn up into a sterile syringe. The 

 needle is passed through a sterile paper and any air present is care- 

 fully expelled. A drop or two of this material can now be injected 

 into another animal. The remainder of the material can be used to 

 make the necessary bacteriological control examinations. In suspected 

 cases the medulla, or brain should be placed in sterile glycerin. In 

 this condition the ^irus retains its virulence for many weeks. The 

 material can thus be transported to a laboratory and examined in the 

 manner indicated. 



