472 THE PLAGUE BACILLUS 



ten days which is a great disadvantage in practice, so that in the majority of cases it is 

 necessary to resort to vaccines (vide ante}. 



(ii) Curative. In treating cases of plague the inoculation of serum should be 

 repeated at intervals, the total volume to be administered being from 200 to 

 400 c.c. It may be inoculated beneath the skin, but intra- venous inoculation gives 

 far better results. As with all other serums, the sooner it is used the better the 

 chance the patient has of recovering. The longer the administration is delayed the 

 larger must be the initial dose of serum given. Generally speaking it is sufficient to 

 inoculate 40-60 c.c. as soon as possible into a vein and to give two further doses 

 (sub-cutaneously of 20-^40 c.c. each time) within the next 24 hours. Daily inocula- 

 tions of 10-40 c.c. should also be given sub-cutaneously until the temperature has 

 fallen to normal. In severe cases Penna obtained good results by giving at the 

 outset 100 c.c. in the veins followed by a daily inoculation into the veins of 

 60100 c.c. This method is to be strongly recommended, many of the failures 

 recorded being due simply to the fact that the serum has been used in too small doses 

 and has been given exclusively beneath the skin. It is important also not to stop 

 the administration of serum suddenly when the fever has subsided but to continue 

 its use for several days in gradually diminishing doses. 



[(&) Rowland prepares a serum which when tested on rats exhibits immuniz- 

 ing, antitoxic and curative properties. 



[A horse is inoculated on several successive occasions with Rowland's " solution 

 B " prepared as above (vide Toxins). The immunizing process lasted over a period 

 of 6 months. The initial dose administered was 0*01 mg. and the final dose 240 mg. 

 The horse was bled twenty- one days after the last inoculation. The local reaction 

 following inoculation was very similar to that following the inoculation of diphtheria 

 toxin : a varying amount of swelling and oedema with transitory constitutional 

 disturbance and a little temperature reaction. There was no tendency to abscess 

 formation or to the huge hard swellings which not infrequently supervene upon 

 the inoculation of unfiltered cultures. 



[The serum neutralizes the toxin in the immunizing solution ; 1'25 c.c. of 

 serum neutralize 100 lethal doses of toxin for the rat. A serum prepared by 

 Yersin's method has no antitoxic action on the toxin. 



[In doses of O'l c.c. the serum protects rats against a subsequent inoculation 

 of the standard test dose of virulent culture given the following day. 



[Administered in doses of 0'5 c.c. sub-cutaneously six hours after inoculation 

 of a living plague culture and on the opposite side of the body to the latter the 

 death rate among rats was reduced from 80 per cent, to 18 per cent, and in 

 those cases in which the treated rats died the length of life was prolonged 

 from three to five days to ten days. In' a comparative experiment with 

 Yersin's serum two rats only out of ten survived while of the ten treated with 

 Rowland's serum all survived and the ten controls which received no serum 

 at all all died.] 



6. Agglutination. 



Plague serum (in dilutions of 1 in 50 to 1 in 500) agglutinates broth cultures 

 of the plague bacillus. The degree of agglutinability of the plague bacillus 

 depends upon the consistency of the culture and not on its virulence 

 (Shibayama). 



The agglutination of the bacillus by the blood of persons suffering from 

 plague is feeble and inconstant. In most cases it can only be effected with 

 dilutions of 1 in 5 or 1 in 20 ; rarely it may be observed in a dilution of 1 in 40. 

 The agglutinating property, which hardly ever appears before the end of the 

 first week of the disease, is most marked in the blood of convalescents and 

 cannot therefore be of any great help in the diagnosis of plague (Zabolotny 

 and Cairus) though it may be useful in diagnosing cases unrecognized in the 

 early stages of the disease. 



