476 Chapter XV 



is made ten to twelve days later and consists of an inoculation of half 

 a cubic centimetre of pure virus. This new method had the special 

 advantage of arresting, almost immediately, the mortality in an in- 

 fected piggery and of eliminating the chronic cases that are some- 

 times observed after the Pasteurian vaccinations. 



Leclainche 1 has already applied his method of serum vaccinations 

 to more than five million pigs of all ages. " It has been found to be 

 constant in its effect and absolutely innocuous," and "not a single 

 case of erysipelas has been met with in pigs that had received the two 

 vaccines," and Leclainche hopes that his method will soon come into 

 general practice, and that it will be utilised in all cases where the 

 Pasteurian method is found to be insufficient. 



As the basis of all the new methods for vaccinating pigs against 

 erysipelas is the preparation of serums capable of preventing the 

 pathogenic effect of the bacilli, the question of the determination of 

 the protective power of these serums comes to be one of considerable 

 importance. At first one was satisfied with certain approximate 

 [499] estimations, but later the necessity was felt of having a more exact 

 measurement. Leclainche is persuaded that of all the laboratory 

 animals capable of being used for these experiments the pigeon is the 

 only one that can usefully fulfil this role ; very susceptible to the 

 passage virus, it is killed by the bacillus after a regular incubation 

 and invasion period, and the chronic form of the erysipelas, so 

 troublesome in the rabbit and even in the pig, is met with in the 

 pigeon in very exceptional cases only. Leclainche commenced his 

 experiments by inoculating into the pectoral muscles of the pigeon 

 mixtures of serum and virulent cultures. The pigeon received 1 c.c. 

 of a culture of a passage virus mixed with variable quantities of 

 serum. The serum is ready for use in the vaccination of pigs when 

 the pigeons resist the injection of a mixture of a c.c. of serum with 

 1 c.c. of a virus which kills the control pigeons in 60 to 72 hours. 



At the Frankfort Institute of Experimental Therapeutics another 

 method of testing devised by Marx 2 is used. In it injections, below 

 the skin of a series of grey mice, are made of progressively increasing 

 doses of the serum the strength of which it is desired to determine. 

 Twenty-four hours later a virulent culture of the bacillus of swine 

 erysipelas is introduced into the peritoneal cavity of the same mice. 

 The virus is so chosen that the control mice die in about 72 hours. 



1 Rev. vet., Toulouse, 1901, t; LVIII, p. 149. 



2 Deutsche thierdrztl. Wchnschr., Karlsruhe, 1901, No. 6. 



