PASTEUR'S TREATMENT FOR RABIES 



421 



infected with rabies. Pasteur found that drying the cord led to a 

 lessening of its virulence, just as certain other conditions increased 

 its virulence. Next he established the fact that subcutaneous 

 injection of a weak virus, followed up with doses of ever-increasingly 

 virulent cords, immunised dogs against infection or inoculation of 

 fully virulent material. From this he reasoned that if he could 

 establish a standard of weakened virulence he would have at hand 

 the necessary " vaccine " for the treatment of the disease. 



Subsequent research and skilled technique resulted in a method 

 of securing this standard, which he found to be a spinal cord dried 

 for fourteen days. The exact details of preparation of this vaccine 

 are as follows: The spinal cords of two 

 rabbits dead of rabies are removed from 

 the spinal canal in their entirety by means 

 of snipping the transverse processes of the 

 vertebrae. Each cord is divided into three 

 more or less equal pieces, and each piece, 

 being snared by a thread of sterilised 

 silk, is carefully suspended in a steril- 

 ised glass jar. At the bottom of the jar 

 is a layer, about half an inch deep, of 

 sterilised calcium chloride. The jars are 

 then removed to a dark chamber, where 

 they are placed at a temperature of 

 20-22° C. in wooden cases. Here they 

 are left to dry. Above each case is a 

 tube of broth, to which has been 

 added a small piece of the corre- 

 sponding cord, in order to test for 

 any micro-organism that may by 

 chance be included. In case of the 

 slightest turbidity in the broth, the 

 cord is rejected. Fourteen series of 

 cords are thus suspended on four- 

 teen consecutive days. The first, second, and third are found to be of 

 practically equal virulence, but from the third to the fourteenth the 

 virulence proportionally decreases, and on the fifteenth day the cord 

 would be practically innocuous and non-virulent. When treatment 

 is to be commenced, obviously the weakest — that is, the fourteenth 

 day — cord is used to make the "vaccine," and so on in steadily 

 increasing doses (as regards virulence) up to, and including, a third- 

 day cord. The fourteenth-day cord is therefore taken, and a small 

 piece cut off and extracted in 10 c.c. of sterile broth, which are 

 placed in a conical glass and covered with two layers of thick filter- 

 paper, the glass with its covering having been previously sterilised 



Fig. 36. — Suspended Spinal Cord. 

 In drying jar contaiuing Calcium Chloride. 



